Chapter XVII: Appendix: B

REMARKS ON MR. CROLL’S THEORY OF SECULAR CHANGES OF THE EARTH’S CLIMATE.

Most scientific readers are familiar with the theory respecting the influence of changes in the eccentricity of the earth’s orbit on the climate of the globe, which has been sustained with remarkable ability by Mr. James Croll. The views originally advanced in various scientific periodicals were presented to the public in a connected form in the volume entitled “Climate and Time,” wherein the author has brought a wide knowledge of the principles of physics, and of the whole field of geological science, to the support of his theory. Even those who have not given especial attention to the subject are also acquainted with the conclusions which Sir Charles Lyell drew from the discussion of Mr. Croll’s arguments, and which are contained in the thirteenth chapter of the tenth edition of his “Principles of Geology,” and also with the more recent examination of the subject which is to be found in Mr. Alfred Wallace’s important work, “Island Life.”

I need not say that a theory so important in its bearing on some of the most obscure problems of geology has been discussed, in more or less detail, by many other writers. To most of the objections presented to his theory, Mr. Croll has replied with his usual ability; and I believe that at present the prevailing tendency among geologists is towards a partial acceptance of his views, subject to the limitations assigned by Mr. Wallace. The latter author holds, in common with Sir Charles Lyell, that geographical causes, arising from the varying distribution of land and sea, have mainly controlled the distribution of temperature over the earth’s surface; but he is disposed to go farther than Lyell in admitting the influence of periods of high eccentricity in causing those great accumulations of snow and ice which were requisite to produce the phenomena of a glacial period, whenever a sufficient area of elevated land in high latitudes coincided with the period of high eccentricity.

It would probably be of little avail, even if I were to undertake the task, that I should attempt any thorough discussion of this vast and difficult problem; and it would certainly require far more space than can here be given to it. I may, however, venture to make a few remarks upon some points which have not, to the best of my knowledge, been much noticed in the discussion.

In reading Mr. Croll’s work, which charmed many an hour during the voyage to and from South America, I found it very difficult to discover any flaw in the chain of close reasoning by which he supports his conclusions. Most of the facts on which he relies are warranted by observation, and have been accepted as well established by writers of the highest authority; and his inferences as to the results of altered conditions appeared to be in strict conformity with admitted physical principles. Nevertheless, when I reflected on the anomalies which are found at the present time in respect to the climate of many spots in the world, and the complexity of the causes which determine its actual condition, I felt a doubt whether, in his attempt to trace the result of possible changes, Mr. Croll may not have overlooked some of the elements of the problem.

Let me briefly state the leading propositions of Mr. Croll’s theory in order to make intelligible the succeeding remarks.

Estimating approximately the mean distance of the earth from the sun at ninety-one and a half millions of miles, and the eccentricity[56] of the sun’s place in the orbit at one and a half million, it follows that at one period of the year, which happens to be about the winter solstice of the northern hemisphere, the earth receives from the sun a quantity of heat greater than that which reaches it in the opposite part of its orbit, in the proportion of 93^2 to 90^2, or about as 1000 to 936. Midsummer of the southern hemisphere is the season when the earth is nearest to the sun; the winter of the southern and the summer of the northern hemisphere occur when the earth is farthest from the source of heat. The conclusion seems inevitable--the southern hemisphere must have hotter summers and colder winters than our hemisphere, where the heat of summer is tempered by the greater distance, and the cold of winter mitigated by the comparative nearness, of the sun.

The next point to be considered is the effect of ocean-currents, and especially of the Gulf-stream, in modifying the climatal conditions of some parts of the earth. Following in the track of the late Captain Maury and Principal Forbes, Mr. Croll has especially insisted on the importance of the great current which, issuing from the Gulf of Mexico, and flowing northward between Florida and the Bahamas, extends across the Atlantic towards the western shores of Europe. He calculates that by this current alone an amount of heat equal to that received on the entire surface of the earth in a zone thirty-two miles in breadth on each side of the equator is carried from the tropics to the cooler regions of the northern hemisphere. Mr. Croll has, I think, victoriously replied to several of the objections opposed to this portion of his argument. His estimate of the volume of water transferred by the Gulf-stream from the tropics to the northern part of the Atlantic, which he reckons at the annual amount of about 166,000 cubic miles, is, I think, in no degree exaggerated; and I also think that he is warranted in estimating the mean initial temperature at about 65° Fahr. I am, however, persuaded that in assuming 40° Fahr. as the temperature to which, on an average, this vast body of water is reduced before it returns to the equatorial zone, Mr. Croll has gone beyond the probable limit. A large part of the stream is diverted eastward about the latitude of the Azores, and is never cooled much below 55° Fahr. before the waters enter the return current on the eastern side of the Atlantic basin; and I believe that, if we allow the water of the Gulf-stream to undergo an average loss of temperature of 20° Fahr., we shall be more likely to exaggerate than to underrate the amount of cooling.

In insisting on the importance of the Gulf-stream in modifying the climate of Europe and the adjacent parts of the arctic zone, Mr. Croll agrees with many preceding writers; but, so far as I know, he was the first to suggest that in consequence of the greater persistency of the south-east trade-winds, which ordinarily extend up to, and, at some seasons, even north of, the equator, the warm waters of the Northern Atlantic derive a large share of the heat which is carried to the temperate and arctic zones from the southern hemisphere. Applying the same reasoning to the currents of the Pacific Ocean, Mr. Croll arrives at the general conclusion (“Climate and Time,” p. 94) that “the amount of heat transferred from the southern hemisphere to the northern is equal to all the heat falling within fifty-two miles on each side of the equator.”

I do not believe that the facts on which Mr. Croll bases this essential portion of his theory are sufficiently established. With regard to the Atlantic, I have expressed in the text (p. 344) an opinion, derived from conversations with practical seamen, that in the Atlantic the trade-winds of the northern are stronger than those of the southern hemisphere. That opinion, I am disposed, on further examination, to regard as incorrect. I believe that the north-east trade-winds often blow with greater force; but, taking the average of the entire year, I now think there can be no doubt that the south-east trade-winds extend over a wider area in the equatorial zone. However this may be, our knowledge of the currents of the Atlantic does not, I think, authorize us to conclude that the portion of heated water carried from the southern to the northern hemisphere is nearly so large as Mr. Croll has estimated. If the heat of the Gulf-stream were mainly supplied, as Mr. Croll contends, from that source, there should be a marked difference in the volume and temperature of the current, between the season when the north-east trade-winds approach the equator and that in which the south-east trades prevail to the north of the line, for which there is no evidence.

As regards the currents and winds of the Pacific, in spite of one considerable exception, to which I shall further allude, I think that the balance of evidence points to a greater prevalence of the south-east trade-winds, and to the probable transference of some portion of the equatorial waters from the southern to the northern hemisphere.

For the present discussion it is best to accept Mr. Croll’s estimate, and to compare the amount of heat which he supposes to be transferred from one hemisphere to the other with the total amount which is received annually from the sun on each hemisphere. For this purpose I have taken the known areas of the torrid, temperate, and frigid zones respectively, and, following Mr. Croll, I have adopted Mr. Meech’s estimate of the average amount of heat, per unit of surface, received from the sun in each zone, irrespective of absorption by the atmosphere. To estimate the proportion of heat which actually reaches the surface, I have adopted Pouillet’s measure of the proportion of solar radiation cut off at vertical incidence, which is 24 per cent. I assume 28 per cent. to be the average loss in the torrid zone, 50 per cent. in the temperate zone, and 75 per cent. in the frigid zone.[57] The resulting figures, showing the proportional amount of heat annually received on the surface of each zone, and on the entire hemisphere, are as follows:--

Torrid zone 3370
Temperate zone 2304
Frigid zone 112
----
Whole hemisphere 5786

Calculating, on the same basis, the amount received on a zone one mile wide at the equator, allowing a loss of 25 per cent. from atmospheric absorption, and multiplying the result by 104, I obtain the number 233·1 or rather more than one twenty-fifth part of the entire heat annually received from the sun by each hemisphere.

To trace the results of such a transfer of heat from one hemisphere to the other, I shall adopt a mode of reasoning, sanctioned by the great authority of Sir John Herschel, to which Mr. Croll frequently resorts. It is by solar heat that the surface of the earth is raised above the temperature of space, which is assumed to be 239 degrees below the zero of Fahrenheit’s scale. Adopting Ferrel’s estimate, I take the mean temperature of the northern hemisphere at 59·5° Fahr., or 298½ degrees above the temperature of space. To maintain this temperature, it receives one-half of the amount of solar radiation which reaches the earth, and in addition, on Mr. Croll’s hypothesis, one twenty-fifth part of that which reaches the southern hemisphere. It follows that the heat available to raise the southern hemisphere above the temperature of space stands to that which is received by the northern hemisphere in the ratio of 24:26, and that the mean temperature of the southern hemisphere should be 298·5 × 12/13, or 275·5° above the temperature of space; so that, in ordinary language, the mean temperature of the southern hemisphere should be 36·5° Fahr. If the fact corresponded with this result of theory, it would not be necessary to invoke increased eccentricity of the earth’s orbit to account for the extreme cold of one hemisphere, seeing that the actual conditions would suffice to completely alter their relative temperatures.

It occurs to me, however, that, on further consideration, Mr. Croll would reduce his estimate of the volume of heated water transferred from the southern to the northern hemisphere; but even if that estimate were reduced by one-half, we ought to find in the southern hemisphere a mean temperature of 47·8° Fahr., or nearly 12 degrees lower than that of our hemisphere.

We have already seen that, so far as climate depends on the relative position of the earth and the sun, we ought to find in the southern hemisphere climates of a more extreme character, with hotter summers and colder winters, than those to which we are accustomed. If it be true that through the agency of ocean-currents a considerable amount of heat is transferred to the northern hemisphere, that circumstance might serve to account for the fact that the summers of the southern are not generally hotter than those of the northern hemisphere; but it would, at the same time, tend to aggravate the severity of the southern winters.

At the time of the publication of Mr. Croll’s earlier memoirs, there existed a general belief that the southern hemisphere was in fact notably cooler than our portion of the globe, and he naturally referred to the supposed fact as harmonizing with the general conclusions drawn by him from theory. But, imperfect as our knowledge of the southern hemisphere still is, a good deal of information has been obtained of late years. The only stations south of the fiftieth degree of latitude from which we possess continuous observations are those mentioned in the text (p. 273); but we also know with sufficient accuracy the climates of two widely separated islands lying about 50° south; and from these we derive results widely different from those to which we were led by theoretical considerations. The following table gives approximately the mean temperatures, on Fahrenheit’s scale, for the year and for the hottest and coldest months of the places referred to in the southern hemisphere, and the means for corresponding latitudes in the northern hemisphere:--

Key:
A: S. latitude.
B: Temperature of January.
C: Temperature of July.
D: Mean of year.
E: N. hemisphere. July.
F: N. hemisphere. January.
G: N. hemisphere. Yearly mean.

--------------------------+-------+-----+-----+-----+-----+-----+-----
| A | B | C | D | E | F | G
--------------------------+-------+-----+-----+-----+-----+-----+-----
Kerguelen Land |49° 17’|44·3°|35·3°|39·6°|63·3°|22·0°|42·9°
Auckland Island |50° 30’|50·2°|35·6°|44·6°|62·3 |19·0°|41·1°
Falklands (Stanley) I.[58]|51° 41’|49·6°|36·5°|43·0°|61·6°|17·1°|39·8°
Falklands II. |52° 5’ |55·9°|37·4°|47·3°|61·3°|16·4°|39·3°
Falklands, mean of I. | | | | | | |
and II. | |52·7°|37·0°|45·1°|61·5°|16·7°|39·6°
Punta Arenas |53° 25’|51·4°|34·7°|43·0°|60·6°|14·2°|37·7°
Ushuaia[59] |54° 53’|53·2°|31·8°|41·9°|59·6°|12·0°|36·2°
--------------------------+-------+-----+-----+-----+-----+-----+-----

If we compare the mean results of these five stations with those for corresponding latitudes in the northern hemisphere, we find that the summers are cooler and the winters very much milder, and that in the latitudes between 50° and 55° the mean annual temperature is notably higher. In Kerguelen Land alone the mean annual temperature is lower than the normal for the same latitude north of the equator; but that island is evidently exposed to exceptional conditions.

The differences between the mean results given above are shown by the following table, in which the signs show the excess or deficiency of the southern as compared with the northern hemisphere:--

Warmest month. Coldest month. Annual mean.
-11·1° Fahr. +18·1° Fahr. +4·2° Fahr.

Dr. Hann has carefully discussed the question as to the comparative mean temperatures of the two hemispheres in a paper published in the proceedings of the Vienna Academy, the substance of which is given in his _Klimatologie_, pp. 89, _et seq._; and it is difficult to refuse assent to his conclusion that so far as the available evidence goes, it shows that the mean temperature of both hemispheres is equal.

I find, then, that the same train of reasoning by which Mr. Croll has sought to explain the occurrence of glacial periods by changes in the eccentricity of the earth’s orbit, and the precession of the equinoxes, leads us to conclusions respecting the climatal condition of the different parts of the earth, at the present amount of eccentricity, which are altogether opposed to the results of observation; and I am driven to the conclusion that the causes which he has adduced have not the predominant influence which he has attributed to them, and that there must be other agencies to which he has not assigned their due importance, but which are adequate to counteract the efficiency of those which, as observation proves, fail to achieve the effects anticipated from them.

I am far from pretending to be able to analyze completely the complex agencies which, by their mutual action, determine the climate of different parts of the earth, but I may briefly refer to two of them. Foremost of these is the relative distribution of land and sea, for a due appreciation of which we are indebted to the great work of Sir Charles Lyell. It is unnecessary here to discuss how far his view of the probable amount of change in past geological epochs may, in the present state of our knowledge, be subject to limitation. Mr. Wallace, who is the most strenuous supporter of the modern doctrine of the permanence of the present continents and ocean basins, recognizes the theoretical correctness of Lyell’s views, and admits that changes of level great enough to cause profound modifications of climate have actually occurred. Notwithstanding recent objections, it appears to me that Darwin’s hypothesis as to the subsidence of a great tract in the Southern Pacific is that which best accounts for the existence of the countless coral islands in that region; nor is the probability of a nearly continuous barrier of volcanic islands across the Atlantic to be completely dismissed. That such changes would have largely affected the climate of the earth cannot, I think, be doubted.

If I may venture to express my own view on this difficult subject, I must say that, although it has not been overlooked by the able men who have discussed it, the paramount importance of aqueous vapour as an agent for modifying climate has not yet been fully recognized. Mr. Croll has constantly discussed the phenomena of ocean-currents, as if their chief function were to affect climate by heating or cooling the surrounding air, which is thence diffused over the land surfaces, and he has devoted little attention to the effects of evaporation from the sea, and the subsequent condensation in some other region of the vapour produced. When we remember that as much heat is consumed in the conversion of one cubic mile of water into vapour as would raise the temperature of nearly ninety-seven cubic miles of water by 10° Fahr., we get some measure of the vast power of vapour as a vehicle of heat. Admitting, as I am disposed to do, that 166,000 cubic miles of water are annually conveyed northward by the Gulf-stream, and suffer an average loss of 20° Fahr. before returning to the torrid zone, I must point out that the entire heat requisite to maintain this great volume of water at the higher temperature would be consumed in the conversion of 3433 cubic miles of water into vapour. In point of fact, I believe that more than one-half of the quantity specified is expended in evaporation, and that the cooling of the waters of the Gulf-stream is mainly due to this agency. To follow the vapour thus produced, to ascertain where it is condensed, and where the heat disengaged in the act of condensation becomes available to raise the temperature of the air, is a task which is beyond our present resources; but it is one which must be performed before we can reason with any confidence as to the ultimate distribution of the heat carried by the Gulf-stream or any other ocean-current. Whatever part of the vapour produced by evaporation from the Gulf-stream goes to supply the rainfall of Western Europe, or to form snow in the arctic regions, acts as a vehicle to transfer heat from the tropics to the temperate and frigid zones. But it is more than probable that a large part of the vapour in question is carried back to the torrid zone, and that some of it is even restored to the southern hemisphere. The south-eastern branch of the Gulf-stream flows, at least partially, into the area of the north-east trade-winds. These winds reach the lower region as cold and very dry winds. As they advance towards the equator, and are gradually warmed, their capacity for aqueous vapour constantly increases, and there can be no doubt that in both hemispheres the trade-winds bear with them a large share of the vapour which goes to supply the heavy rainfall of the tropics.

In the Pacific region we have direct evidence to this effect, in the fact that in Hawaii, and elsewhere, the side of the islands exposed to the trade-winds is that of heavy rainfall, and is generally covered with forest. No sufficient data exist for estimating the amount of vapour thus carried back to the tropics from high latitudes on both sides of the equator, nor the amount of heat set free by its condensation; but we may form some conception of its probable amount by considering that at the moderate estimate of a mean annual rainfall of seventy-two inches for the portion of the globe between the tropics, this amounts to a yearly fall of 88,737 cubic miles, and that we can scarcely reckon the share of this great volume of water supplied by evaporation from the same part of the globe at more than one-half. Still less is it possible to calculate the amount of vapour annually transferred from the northern to the southern hemisphere, which goes to neutralize the apparent effect of the diversion of portions of the equatorial waters to the north side of the line. In the Atlantic basin it is probable that the larger part of the rainfall in the region including and surrounding the Gulf of Mexico and the Caribbean Sea is supplied by vapour carried from the temperate zone by the north-east trade-winds. There is some reason to believe that a portion of the rainfall of the great basin of the Amazons, south of the line, is also supplied from the same source. Several travellers report that during the rainy season the prevailing winds are from the west and north-west, the latter being especially predominant at Iquitos, about 4° S. latitude, and 1600 miles from the mouth of the river.

In tropical Australia the rainy season falls during the prevalence of the north-west monsoon, and we cannot doubt that this is mainly supplied by vapour carried from the northern hemisphere. Another region wherein the same phenomenon is exhibited on a large scale is the central portion of Polynesia, extending from the Feejee to the Society Islands over a space of at least twenty degrees of longitude. Over that wide area, as far as about twenty degrees south of the line, the regular south-east trade-wind prevails only in the winter of the southern hemisphere, while during the rest of the year, especially in summer, north and north-east winds have the predominance. Taking the mean of three stations in the Feejee Islands, of which the returns are given by Dr. Hann, I find in round numbers the very large amount of 150 inches for the mean annual rainfall, of which 105 fall during the seven months from October to April, while the five colder months from May to September supply only forty-five inches of rain. There can be little doubt that the larger part of the 105 inches falling during the warm season is derived from the northern hemisphere.

I by no means seek to account fully for the apparent contradiction between the results of theory, as developed by Dr. Croll, and the actual distribution of heat over the earth as proved by observation; but I venture to think that I have shown reason to doubt the possibility of drawing absolute conclusions as to the results of astronomical changes until we shall have fuller knowledge than we now possess of all the agencies that regulate climates.

Before concluding these remarks, I will notice one other branch of the argument in regard to which I am unable to concur with Mr. Croll. As we have seen, the essential point in his theory as to the _modus operandi_ of changes of eccentricity, and the relative position of the poles, on the distribution of temperature, is that the currents of the equatorial zone are driven towards the pole which has the summer in aphelion, and that the cause of this shifting of the currents depends on the greater strength of the trade-winds in the hemisphere which has the winter in aphelion; the strength of the trade-winds in turn depending on the amount of difference of temperature between the equatorial and the colder zones. Taking the surface of the earth generally, the trade-winds of the southern are probably stronger than those of the northern hemisphere, and, if it were true that the south temperate and frigid zones were colder than those of the other hemisphere, it would be allowable to argue that the greater difference of temperature as compared with the equatorial zone was the cause of the greater strength of the trade-winds. But we now certainly know that the southern hemisphere between latitudes 45° and 55° is considerably warmer than the corresponding zone of the northern hemisphere, and we have good grounds for believing that the mean temperature of the whole hemisphere south of latitude 45° is higher, and certainly not lower, than that of the same portion of the northern hemisphere. We are therefore not justified in explaining the greater strength of the southern trade-winds by a greater inequality of temperature between the equator and the pole.

In my opinion the cause of this predominance of the southern trade-winds is to be sought in the fact that the southern is mainly a water hemisphere, while the northern is in great part a land hemisphere. In the south, the great currents of the atmosphere flow with scarcely any interruption, except that caused by Australia, where, in fact, the trade-winds are irregular, and lose their force. In the northern hemisphere the various winds originating in the unequal heating of the land surface interfere with the normal force of the trade-winds, and weaken their effect.

In connection with this branch of the subject, I may remark that the belief in the greater cold of the southern hemisphere mainly rests on the fact that all the land hitherto seen in high latitudes has been mountainous, and is covered by great accumulations of snow and ice. But this does not in itself justify the conclusion that the mean temperature is extremely low. It is true that the fogs which ordinarily rest on a snow-covered surface much diminish the effect of solar radiation during the summer in high latitudes, but this is compensated by the great amount of heat liberated in the condensation of vapour. The only part of the earth which is now believed to be covered with an ice-sheet is Greenland, but the mean of the observations in that country shows a temperature higher by at least 10° Fahr. than that of Northern Asia, where the amount of snowfall is very slight, and rapidly disappears during the short arctic summer. If there be, as some persons believe, a large tract of continental land surrounding the south pole, I should expect to find that the great accumulations of snow and ice are confined to the coast regions. In that case the mean temperature of the region within the antarctic circle would probably be lower than it would be in the supposition, which appears to me more probable, that the lands hitherto seen belong to scattered mountainous islands. If, from any combination of causes, one pole of the earth has ever been brought to a mean temperature much lower than that now experienced, I should expect to find that the phenomena of glaciation would be exhibited towards the equatorial limit of the cold zone, rather than in the portions near the pole. The formation of land-ice depends on the condensation of vapour, and before air-currents could reach the centre of an area of extreme cold the contained vapour would have been condensed. This consideration alone suffices, to my mind, to make the supposition of a polar ice-cap in the highest degree improbable.

Mr. Wallace (“Island Life,” p. 142) cites, as conclusive evidence of the effect of winter in aphelion in producing glaciation, the facts, to which attention was first directed by Darwin, as to the depression of the line of perpetual snow, and the consequent extension of great glaciers, on the west coast of Southern Chili. I have adverted to this subject in the text (p. 229), and I may further remark that if winter in aphelion be the cause of the depression of the snow-line in latitude 41° S., it can scarcely fail to produce some similar effect in latitude 34° S. Yet we find on the southern limit the snow-line much lower, and at the northern much higher, than it has ever been observed in corresponding latitudes in the northern hemisphere, the line being depressed by more than 8000 feet within a distance of only seven degrees of latitude. The explanation, as I have ventured to maintain, is altogether to be found in the extraordinary rainfall of Southern Chili; and to the same cause we must attribute the fact that, in spite of the greater distance of the sun, the winter temperature is higher than in most places in corresponding latitudes in the northern hemisphere. At Ancud in Chiloe, in latitude 41° 46′, the temperature of the coldest month is lower by less than three and a half degrees of Fahrenheit than it is at Coimbra in Portugal, one and a half degree nearer the equator, in the region which receives the full warming effect of the Gulf-stream.

I should have expressed myself ill in the preceding pages if I should be supposed to deny that, in his writings on this subject, Mr. Croll has made an important contribution to the physics of geology. He has, in my humble opinion, been the first to recognize the full importance of one of the agencies which, under possible conditions, may have profoundly affected the climate of the globe during past epochs, although I do not believe that, in the present state of our knowledge, we can safely draw those positive inferences at which he has arrived. Even those who are unable to accept any portion of his theory as to the causes of past changes of climate must feel indebted to his writings for numerous valuable suggestions, and for the removal of many popular opinions which his acute criticism has shown to be untenable.

INDEX.

A

_Acacia Cavenia_, 157

Aconcagua, 192

---- valley, vegetation of, 195

_Adesmia_, 182

Agassiz, Professor Alexander, 342

Ajulla, Promontory of, 51

Albatross, 215

Alligators, 41

Alpine zone in Andes, 91

Amancais, 71

Amatapi, Sierra, 52

Ancud, 145

Andean Flora, Alpine zone, 104

----, divisions of the, 104

----, European genera common to, 101

Andean railways, 63

Andes, 49

----, Alpine zone in, 91

----, cactoid plant in, 92

----, Chilian, view of, 183

----, climate of Peruvian, 99

----, _Compositæ_ in, 102

----, cosmopolitan weeds in, 101

Aneroid barometers, 353, 354

Angol, 213

Antarctic beech, 256

---- Flora, range of, 219

_Anthopterus Wardii_, 34

Anticosti, 273

Apoquinto, baths of, 188

Araucanian Indians, 212

----, language of, 213

_Araucaria Brasiliensis_, 311

Argentaria, climate of, 300

----, emigration to, 298, 299

----, forests of, 295

----, progress of agriculture, 298

----, frontier of Chili and, 258

Arica, vegetation of, 121

_Armeria maritima_, var. _andina_, 263

Artichoke, wild, 168

Atacama, desert of, 124, 131

Atlantic, colour of, 7

----, summer temperature of, 362

----, temperature of, 5

----, winds of, 345

_Ayacucho_ steamship, 118

Azores, 5

B

_Baccharis_, 157

Bahia Blanca, 298, 357, 358

Bahia de Todos Santos, 346

_Baillonia spartioides_, 202

Balmacedo, Don F., 191

Banda Oriental, 281

----, vegetation of, 293

Barbadoes, absence of venomous snakes in, 14

----, black population of, 11

---- harbour police, 9

---- planters, 13

----, productiveness of, 8

Barometer, high, 4

----, tables for, 4

Beagle Channel, 273

Belem, Tower of, 363

_Berberis buxifolia_, 263

---- _empetrifolia_, 263

---- _ilicifolia_, 263

Berberry, 225

Bentos, Fray, 287

Bio-Bio river, 213

Black-fish, 7

Blue Mountains, Jamaica, 17

_Bombax pubescens_, 328

Borya Bay, 241

Bossi, Signor Bartolomeo, 281

Botafogo, 322

Bove, Lieutenant, 252

Bramble in Chili, 150

Brazil, ancient mountains of, 317

----, coffee-planting in, 341

----, geology of, 313, 314

----, glacial deposits in, 342

----, rainfall in coast region of, 334

Brazilian physicians, their fees, 340

Bridges, suspension, in the Andes, 85

Buenaventura, 32

Buenos Ayres, 293-295, 299

C

Cabo Blanco, 43

---- San Lorenzo, 37

---- Santa Elena, 38

Cachapoal river, 178

Cactoid plant in Andes, 92

Caldera, 133

Callao, 61

----, quarantine at, 57

Canary Islands, 362

Cape Froward, 243

---- Parinas, 44

---- pigeon (_Daption capensis_), 214

---- Pillar, 238

---- Verde Islands, 359

Capricorn, Tropic of, 132

Cardoon, 164

Casapalta, 91

Catamarans, 352

_Cathartes atratus_, 112

Caudivilla, 109

Cauquenes, Morro de, 182

----, town of, 169

Cauquenes Baths, 172

----, railway to, 163

Celery, wild, 221

_Cereus Quisco_, 151, 176

Cerro de Pasco, 72

---- del Roble, 151

Chacao, Canal de, 216

Chagres river, 22

Chañeral, 133

Channels of Patagonia, 222, 223

Chicla, hotel at, 80

----, scenery at, 84

----, vegetation of, 98

Chili and Argentaria, frontier of, 258

---- and Peru, naval war of, 58

----, bramble in, 150

----, Central, flora of, 141

---- ----, climate of, 143-145

---- ----, rainfall in, 144

----, European plants in, 164

----, physical geography of, 170

----, Southern, glaciers of, 229

---- ----, rainfall of, 229

Chilian elections, cumulative vote, 191

---- mines, 161

_Chiliotrichium amelloides_, 234

Chiloe, island of, 215

Chimborazo, 38

Chonos Archipelago, 216

Chosica, 73

_Chuquiraga spinosa_, 91

Churches in Lima, 62

_Chusquea_, 152

Cigars, Guayaquil, 41

Cinnamon tree, 10

Claraz, M. Georges, 357, 358

Clarence Island, 243

Climate, effects of tropical, 39

_Cnicus lanceolatus_, 164

Cobeja, 131

Coffee-planting in Brazil, 341

_Colletia spinosa_, 177

Colomba, 214

Colon, 21, 22, 27

Commercial travellers, German, 309

_Compositæ_ in Andes, 102

Concepcion del Uruguay, 288

Condor, 87, 93

Condors, captive, 185

Copiapò, 133

----, Rio de, 133

Coquimbo, vegetation of, 136, 138

Corbett, Mr., 328

Cordillera de la Costa, 218

Cordillera Grande, of Goyaz, 315

Cordillera Pelada, 218, 219

Cordillera in Peru, 49

Corrientes, 294, 300

Cosmos Line, German steamers of, 205

Cousiño, Madame, 207

Crab, red, 227

Croll, Dr. James, 271

----, remarks on his theory of secular changes of climate, 393

_Cryptocarya Peumus_, 160

Cuyabà, 279, 310

D

Dandelion (_Taraxacum lævigatum_), 263

_Daption capensis_, 214

Darwin, Mount, 267, 270

Dawson Island, 245

_Desfontainea spinosa_, 225

Desolation, Land of, 235, 241

_Diomedea exulans_, 215

---- _fuliginosa_, 215

_Don_, Royal Mail steamer, 2

_Doterel_, wreck of the, 267

_Drimys Winteri_, 147

Drummond-Hay, Mr., 148

Dungeness, 271

_Duvaua dependens_, 293

E

Earthquake-waves, 122

_Eccremocarpus scaber_, 199

Ecuador, 36, 40

Eden harbour, 224

Education, Chilian zeal for, 265

Elections, Chilian, cumulative vote, 191

_Encelia canescens_, 134

Engler, Dr., 34, 106

English Narrows, 223

English the _lingua franca_ of America, 88

Ensenada, 302

Entrerios, 288

Equator, cold current near, 356

----, path of the sun, 37

Equatorial rains, 352

---- vegetation, 33

_Erodium cicutarium_, 165

_Escallonia_, 181

Espiritu Santo, Cape, 271

_Eucalyptus globulus_, 160, 292

Evergreen beech (_Fagus betuloides_), 225

Existence, struggle for, 330

Eyre Sound, 228

F

_Fagus betuloides_, 225

---- _obliqua_, 151

Falkland Islands, 247, 273

Fayrer, Sir Joseph, 349

Fenton, Dr., 250, 262, 269

Fernando Noronha, 354, 355

Feuillée, Father, 184

Flint, Mr., 153

Flowering plants, origin of, 318

Flying-fish, 5

---- of Pacific, 53

Fogs on Peruvian coast, 54

_Francoa sonchifolia_, 210

French, Dr., 289, 291

Fruit-sellers, migratory, 42

Fuegians, 233, 242, 260, 261

G

Gallinazo, 87

----, scavenger bird, 112

_Galvesia limensis_, 45

Gillies, Captain, 344

Glacial deposits in Brazil, 342

Glaciers in South Patagonia, 239

---- of Southern Chili, 229

Glaziou, Dr., 324

_Gleichenia_, 226, 311

_Glyptodon_, 358

Gongo Seco, 316

Gordontown, Jamaica, 18

----, cool climate of, 19

Graham, Mr. J. R., 67

Granite, disintegration of, 315

Grisebach, 34, 145

Gualtro, 168

Guanacos, 131, 253

Guano Islands, 53

Guayaquil cigars, 41

Guayaquil, city of, 40, 41

----, Gulf of, 38, 40

Guayas river, 38, 41, 42

_Gynopleura linearifolia_, 157

H

Hale Cove, 220

Hann, Dr. Julius, 144, 305, 349

Hanover Island, 236

Hayti, island of, 15

----, cannibalism in, 16

Haze, opacity of, 158

Heights above sea-level, fall of temperature in ascending to, 369

Henderson’s Inlet, 231

Hess, Mr., 163

_Hippeastrum equestre_, 19

Hopedale, in Labrador, 273

Huanillos, 127

Humboldt current, 50

Humming-birds, 209

_Hura crepitans_, 10

_Hymenophylla_, 226

I

_Iberia_ steamship, 269

Ice-axe, 226

Ice, floating, 228

Illiluk, 274

Immigrant plants, Darwin’s view of, 166

----, checks on their extension, 167

Indians, Araucanian, 212

----, Patagonian, 260

Iquique, 121

----, sea-fight at, 127

Isla de Santa Maria, 211

_Islay_ steamship, 29

Itamariti, Falls of, 329

J

Jamaica, 16

----, black population of, 20

----, vegetation of, 18

Jacmel harbour, 15

K

_Kageneckia oblonga_, 175

Kingston, Jamaica, 16

L

_Lapageria rosea_, 209

La Plata, estuary of, 277, 283

Las Condes, 163

La Serena, 136, 145

Lavapie Promontory, 211

Liais, M., 342

_Libocedrus_, 235

Lichens, 221

Lima, 61

----, a dinner-party at, 108

----, ancient beaches near, 113

----, meteorological observations at, 99

_Liriodendron_, 344

Lisbon, Rock of, 363

Llaillai, 150

Llama in Peru, 95

Loa river, 127

_Lobelia gigantea_, 184

_Lobelia tupa_, 184

----, poisonous species of, 76

Lobos de tierra, 53

---- de afuera, 53

_Lomaria magellanica_, 226

Lombardi, Signor M., 109

Lombardy poplar, 160

_Loranthus_, 176, 202

Lord Nelson Strait, 236

Lota, coal deposits of, 207

----, parque of, 208

Lynch, Don Patricio, 67

----, his administration, 68

M

Maceio, 347

Magellan, Straits of, 238, 239, 367

----, forests in the, 240

----, variable climate in, 240, 254

Maipo river, 134

Maldonado, 304

_Malesherbiaceæ_, 157

Mango tree, 10

Mapocho river, 157

Markham, Captain Albert, 135

_Marrubium vulgare_, 138

Matto Grosso, 279

Matucana, San Juan de, 76

Mayne Channel, 237

_Maytenus magellanica_, 263

Meiggs, Mr., 65

Mejillones, 132

Memory, lapses of, 26

Mendoza, 300

Mercator’s projection, 30

Messier’s Channel, 220, 231

Mist, clearing of, 333

_Mitraria coccinea_, 225

Molina, 175

Mollendo, 119

----, a bad port, 120

Monkeys, domesticated, 332

Monson, Mr., 280

Montaña of Eastern Peru, 97

Monte Video, 277, 279

Morro de Cauquenes, 182

Mountain-sickness, 81

_Mulinum_, 189

_Mutisia_, 177

_Mutisiaceæ_, 102

_Myzodendron punctulatum_, 256

N

Napp, Mr. Richard, 300

Nation, Mr. W., 70, 108

Naval war of Chili and Peru, 58

New Granada, 32

_Nicotiana glauca_, 360

Nikolaiewsk, 273

North Atlantic, trade-wind of, 361

Northern hemisphere, temperature of, 273, 274

O

O’Higgins, General, 154

Olfactory nerve, fugitive impressions, 190

_Oreodoxa regia_, 324

Organ Mountains, 325

Oroya railway, 64

----, spiral tunnel of, 79

----, viaducts of, 74

Ostrich, South American, 261

_Oxalis lobata_, 146

P

Pacific coast-steamers, 31

Pacific, colour of water of, 31

----, first view of, 25

----, flying-fish of, 53

----, high seas in Southern, 211

---- steamer, delay of, 269

Paisandu, 288, 289

Palms, avenue of, 323

Panama, 21

---- Bay, birds in, 29

---- Grand Hotel, 27

---- railway, 25

---- ship-canal, 23

----, vegetation of, 24

Paraguay river-steamers, 279

Paranà, 317

----, basin of the, 312

---- river, 284

Paranagua, Bay of, 308

Paranahyba, 313

---- valley, 320

Parasites and climbers, 330

Patagonia, 300

---- Channels, scenery of, 222, 227

----, vegetation of, 225, 235

----, women of, 253

Patagonian coast, winter climate, 276

Patagonian Indians, 260

Payta, climate and vegetation of, 45

Peckett Harbour, 262, 270

Pedro, Dom, Emperor of Brazil, 337

Pelicans, black, 59

Peñas, Gulf of, 218

Pernambuco, 351

_Pernettya_, 225

Peru, 44

---- and Chili, naval war of, 58

----, climate of Northern, 47

----, future of, 117

Peruvian coast, fogs on, 54

----, low temperature of, 55

---- sugar-plantation, 110

Pessimism, 365, 366

Petrel, giant, 215

Petropolis, 326, 327, 335

----, hermit of, 331

----, winter climate of, 334

Peumo tree, 159, 175

Philippi, Dr., 154

----, Professor Federigo, 155, 219

Physicians, Brazilian, their fees, 340

Pierola, Dictator of Peru, 117

Pietrabona, Commander, 257

Pimento tree, 10

Pisagua, 123

----, white rocks at, 125

Pisco, 119

_Plantago maritima_, 263

_Pleroma arboreum_, 342

---- _granulosum_, 336

_Podocarpus nubigena_, 235

Poncho, 179

_Porliera hygrometrica_, 199

Port Famine, 245, 250

---- Gallant, 241

Potato, wild, in Andes, 93

Prado, General, 36

_Prosopis limensis_, 46

_Proustia Baccharoides_, 195

_Pteris aquilina_, 329

Puente Infernillo, 78

Puerto Bueno, 233

Punta Arenas, 145, 246, 273

_Puya_, 151

Q

Quadras in Santiago, 153

Quarantine at Callao, 57

---- at St. Vincent, 359

_Quaresma_, 336

Queen Adelaide Island, 236, 238

_Quillaja saponaria_, 175

Quillota, Valley of, 150

Quinta Normal at Santiago, 155

R

Railways, Andean, 63

----, Oroya, 64

----, spiral tunnel of, 79

----, viaducts of, 74

Rancagua, 168

Reed, Mr. Edwin, 204

Reilly, Mr., 210

Resguardo del Rio Colorado, 200

_Rhamses_, the, 205

_Rhea Darwinii_, habits of, 261

Rimac, valley of the, 71

----, ancient terraces in, 75

----, _Compositæ_ in, 76

----, effects of sea-breeze in, 98

Rio Claro, 171

---- Colorado, 276

---- Janeiro, Bay of, 321, 322, 325

---- Parahyba do Sul, 313

---- San Francisco, 314

Rocks, disintegration of, 115

----, ice-action on, 228

_Rumex acetosella_, 263

S

_Sagittaria Montevidensis_, 297

Saladeros, 287

_Salix Humboldtiana_, 77

Salta, 294

Salto, 291

_Sambucus Peruviana_, 101

Sampayo, Don Francisco, 257

San Bartolomé, 73

---- Cristobal, Cerro, 156

Sand-box tree (_Hura crepitans_), 10

Sandy Point, 246, 250

----, burnt forest at, 256

----, mutiny of convicts at, 251

----, the hotel at, 249

----, vegetation of, 255, 263

San Felipe, 192

Sanitary rules, neglect of, 87

San José, Promontory of, 276

---- volcano, 164

San Lorenzo, island of, 59

San Matias, Bay of, 276

San Paulo, 308-310

---- and Rio Janeiro railway, 312

----, railway from Santos to, 307, 308

San Ramon, Salto de, 190

Santa Clara, 72

Santa Cruz settlement, 246

Santa Lucia, Rock of, 162

Santa Rosa de los Andes, 193, 196

Santiago, 145, 153, 156, 161

----, railway to, 149

----, sunset at, 186

Santos, 305, 306

----, tropical vegetation at, 307

São João da Barra, 312

São Salvador, 346

Sarmiento Channel, 231

Sarmiento, Mount, 243, 244, 267, 270

Scavenger bird, 112

_Schinus molle_, 77

Sea-sickness, 217

Seaweed, bands of, 6

_Senecio_, the genus, 268

Serra da Mantiqueira, 313, 314

Serra do Mar, 308, 314

Shannon, Captain, 269

Simpson, Captain, 207

Sitka, 274

Smyth’s Channel, 231, 237

_Solanum mammosum_, 33

Soroche, mountain-sickness, 81

Soto, Don Olegario, 171

South America, tropical, origin of flora, 35

----, rainless zone of, 48

South Brazil, plateau of, flora, 311

South Patagonia, glaciers in, 239

Southern Atlantic, climate of, 305

Southern Cross, 7, 253

Southern hemisphere, temperature of, 272-274

Spanish-Americans, indolence of, 89

Species, groups of incomplete, 181

Staten Island, 252, 258

St. Antão Island, 359

Steamers, Pacific coast, 31

Straits of Magellan, 270

Sunstroke, causes of, 349, 350

Surco station, 75

Swinburne, Don Carlos, 154

T

Taforò, Dr., 191

_Tagus_ steamship, 344

Talca, 145

Taltal, 133

Tamar, Cape, 240

Tambo de Mora, 119

Tarapacà, 125

_Taraxacum lævigatum_, 263

Telephone, use of, in South America, 290

Tierra del Fuego, 245, 267

Tijuca, 338

----, giant tree near, 343

----, vegetation of, 341

_Tillandsia_, 307

Titicaca, Lake of, 63, 66

Tocantins river, 315

Tocopilla, 128, 133

----, scenery of the moon, 129

Trade wind, north-east, 6

Trescott, Mr., 60

Tres Montes, Cape, 218

Trinidad, Gulf of, 231

_Triumph_, the ship, 135

_Tropæolum tuberosum_, 78

Trumpet-flower (_Bignonia venusta_), 307, 311

Tucuman, 294

Tumaco, 36

Tumbez, 43

_Tupa Berterii_, 184

---- _secunda_, 184

Tupungato, the Peak of, 153

U

Ucayali river, English settler at, 96

Unalaschka, 274

Uruguay, climate of, 279

----, fossil remains in, 291

----, islands of the, 287

---- Republic of, chronic disorder, 282, 284, 285

Ushuaia, mission station at, 260

Ushuaja, 273

Uspallata Pass, 200

_Utricularia_, 33

V

Valdivia, 145

Valparaiso, 138, 145

----, danger of earthquakes at, 139

Vegetation, equatorial, 33

Verbena family, 201

Viaducts, Oroya railway, 74

Vicuña Mackenna, Don Benjamin, 158

Villages, remains of ancient Peruvian, 73

Viña del Mar, 149

Vincent, St., aspect of, 360

----, quarantine at, 359

Vinciguerra, Signor, 252

Virgenes, Cape, 271

Volcano de Chana, 219

W

Wellington Island, 222

Willsen, Captain, 205

Winter’s bark (_Drimys Winteri_), 147

Y

Yellow fever, treatment of, 339

NOTE ON THE MAP OF SOUTH AMERICA.

In the annexed map an attempt has been made to represent the probable course of the isothermal lines--lines denoting equal temperature--in the South American continent. The black lines indicate the mean temperature for the entire year; the red lines that for January, the hottest month; and the green lines that of July, the coldest month. The numbers placed over each line in corresponding colours indicate the temperature in degrees of the Centigrade scale. We possess a fair amount of information as to the meteorology of the coasts of the continent; but of the interior our knowledge is miserably deficient, and is nearly limited to several stations in Argentaria, and a few in the basin of the Amazons. As a result, the course of the isothermal lines in the interior is to a great extent conjectural. As in all similar maps, no account has been taken of the relief of the surface; when a line crosses a mountain range, the temperature indicated is that which would be found, as is assumed, if the height were reduced to the sea-level. No attempt has been made to show the variations of temperature with the season in the part of the continent near the equator. These are very slight, and depend mainly on local conditions, the mean temperature of the year varying from 25·5° to 28° C., or from about 78° to 82° Fahr.; the hottest seasons near the equator, apart from local conditions, being those of the equinoxes.

The chief interest of the map to the physical geographer arises from the remarkable effect of the southern, or Humboldt, current, in lowering the temperature of the western coast between the fifth and the fortieth degrees of south latitude. This is, of course, most apparent in the isothermal for January. It will be seen that at that season the temperature of Northern Peru is about the same as that of Buenos Ayres, lying thirty degrees farther from the equator. In mid-winter (July) the effect is far less apparent, and in the south of the continent the isotherms for that season nearly correspond with the parallels of latitude. The lines indicating mean annual temperature naturally assume a course intermediate between those for the extreme seasons.

PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.

Edw^{d.} Weller, lith.
_London: Kegan Paul, Trench & Co._

SOUTH AMERICA
illustrating the
NOTES OF A NATURALIST.
]

FOOTNOTES

[1] For a list of the plants collected here, see a paper in the _Journal of the Linnæan Society_, vol. xxii.

[2] Much cinchona bark, coming from the interior, was formerly shipped at Tumaco; but between horrible roads and the reckless waste of the forests through mismanagement, but little is now conveyed by this way.

[3] For a list of the species collected, see the _Journal of Linnæan Society_, vol. xxii.

[4] The abrupt change in the vegetation on this part of the American coast has been noticed by Humboldt, Weddell, and other scientific travellers. In a note to the French edition of Grisebach (“Vegetation du Globe,” traduit par P. de Tchihatcheff, ii. p. 615), M. André expresses the opinion that this, as well as some other cases of abrupt change in the vegetation observed by him in Colombia, are to be explained by the nature of the soil, which in the arid tracts is sandy or stony, and fails to retain moisture. Admitting that in certain cases this may afford a partial explanation of the facts, it is scarcely conceivable that the limit of the zone wherein little or no rain falls should exactly coincide with a change in the constitution of the soil, and I should be more disposed to admit a reversed order of causation, the porous and mobile superficial crust remaining in those tracts where, owing to deficient rainfall, there is no formation of vegetable mould, and no accumulation of the finer sediment forming a retentive clay.

[5] The only detailed account of the operations that I have seen is in a work entitled, “Histoire de la Guerre du Pacifique,” by Don Diego Barros Arana. Paris: 1881. It appears to be fairly accurate as to facts, but coloured by very decided Chilian sympathies.

[6] The heights given in the text are those of the railway stations.

[7] Of 138 genera of _Helianthoïdeæ_ 107 are exclusively confined to the American continent, 18 more are common to America and distant regions of the earth, one only is limited to tropical Asia, and two to tropical Africa, the remainder being scattered among remote islands--the Sandwich group, the Galapagos, Madagascar, and St. Helena.

[8] See note to page 184.

[9] In _Nature_ for September 14, 1882.

[10] The only accurate information that I have found respecting the climate of Lima is contained in a paper by Rouand y Paz Soldan, “Resumen de las Observaciones Meteorologicas hechas en Lima durante 1869,” quoted in the French translation of Grisebach’s “Vegetation du Globe.” Reduced to English measures, they give the following results:--

Mean temperature of four years 66·6° Fahr.
” ” January, 1869 74·3° ”
” ” July, 1869 57·6° ”
Rainfall in the year 1869 13·4 inches.
” June, 1869 2·45 ”
” July, 1869 2·72 ”
” August, 1869 2·48 ”
” September, 1869 2·33 ”
” October, 1869 2·16 ”
” remaining seven months 1·24 ”

There is reason to think that the temperature for July, 1869, given above was exceptionally low, and although the months during which fogs prevail are abnormally cool for a place within 13° of the equator, I believe that the thermometer rarely falls below 60° Fahr.

[11] See Appendix A, On the Fall of Temperature in ascending to Heights above the Sea-level.

[12] It is a curious illustration of the utterly untrustworthy character of statements made by unscientific travellers to read the following passage in a book published by a recent traveller in South America, who visited Chicla in November, the beginning of summer. He declares that the fringe of green vegetation “dwindles and withers at a height of nine or ten thousand feet;... while on the upper grounds, where sometimes rain is plentiful, the air is too keen and cold for even the most dwarfish and stunted vegetation to thrive.”

[13] “Versuch einer Entwicklungsgeschichte der Pflanzenwelt.”

[14] The heights are certainly incorrect. The base of the hill of Amancaes is nearly seven hundred feet above sea-level, and Mr. Nation states that the two localities mentioned by Mr. Cruikshank are at about the same elevation.

[15] Two small Chilian wooden ships, the _Esmeralda_, of 850 tons, mounting eight guns, commanded by Arturo Prat, and the _Covadonga_, of 412 tons, with two guns, commanded by Condell, were engaged in the blockade of Iquique, when, on the 21st of May, 1879, they were attacked by the Peruvian ironclad _Independencia_, of 2004 tons, mounting 18 (chiefly heavy Armstrong) guns, commanded by J. G. Moore, and the monitor _Huascar_, of 1130 tons, mounting two 300-pounder Armstrong turret guns, besides two deck guns, under Miguel Grau, the most skilful and enterprising of the Peruvian commanders. The Chilian captains resolved on a desperate defence. After maintaining for two hours the fight against the _Huascar_, Arturo Prat resolved on the attempt to board his adversary. Bringing his ship alongside, he sprang on the deck of the _Huascar_; but the ships were separated at once, and two men only fell along with him, while the _Esmeralda_ went to the bottom with her crew of 180 men, of whom several were picked up by the boats of the _Huascar_. The _Independencia_, following the little _Covadonga_, ran on the rocks in the shallows south of Iquique, and became a total wreck; while the _Covadonga_, though shattered by her enemy’s guns, was able to reach Autofogasta. The heroism of the Chilian commanders saved their country, and at the critical moment changed the fortune of the war.

[16] In the preface to his “Florula Atacamensis,” Dr. Philippi, who has explored this region more thoroughly than any other traveller, states that on the range of coast hills between the Pan de Azucar (lat. 26° 8′ south) and Miguel Diaz (lat. 24° 36′) the fogs, called in Peru _garua_, or _garruga_, deposit during a great part of the year some moisture which occasionally takes the form of fine rain, such as is familiarly known to occur on the hills near Lima. He remarks as singular the fact that the same phenomenon is not observed on the coast north or south of those limits. From more recent observations, it would appear that this is not strictly true as regards the higher coast hills near Coquimbo, but it seems to hold as regards the tract of coast to the northward, between the neighbourhood of Taltal and that of Iquique, a distance of about four degrees of latitude. It may be that the coast hills are lower here than further south, and that as the desert region inland rises very gradually, and has a higher temperature inland than near the coast, the formation of fog is prevented. Whatever be the cause, the absence of fog would go far to account for the utter sterility of this region.

[17] The four species of _Encelia_ described in De Candolle’s “Prodromus” appear to me to be but slightly modified forms of a single species. Since the publication of that work, several other and quite distinct species have been ranked under the same generic name.

[18] While botanizing in the Tajo de Ronda, the singular cleft which cuts through the rocky hill on which the town is built, I was once for some time in positive danger. The boys, having espied me, assembled on the bridge that crosses the cleft, some three hundred feet above my head, and commenced a regular fire of stones, that drove me to take shelter under an overhanging rock until, being tired of the sport, they turned their attentions elsewhere.

[19] One of the difficulties felt by all students of geographical distribution arises from the imperfect or careless indications given both in books and in herbaria, and this is more felt in regard to South America than as to any other part of the world. A very large proportion of the earlier collections bear simply the label “Brazil,” forgetting that the area is as great as that of Europe. In other cases local names of places, not to be found on maps or in gazetteers, embarrass the student and weary his patience. It is mainly from Darwin that naturalists have learned that geographical distribution is the chief key to the past history of the earth.

[20] The last season of excessive rainfall was that of 1877. I have seen no complete returns, but it appears that the rain of that year commenced in Central Chili in February, a very rare phenomenon; that more than six inches of rain fell in April, of which, at Santiago, four inches fell in twenty-four hours. More heavy rain fell in May, and finally in July a succession of storms flooded large districts, destroying property and life, the fall for the month being more than fourteen inches at Valparaiso. Much interesting information respecting the climate of Chili will be found in a work by Don B. Vicuña Mackenna, “Ensayo Historico sobre el Clima de Chile” (Valparaiso: 1877), from which I have borrowed the above-mentioned particulars.

[21] I believe that in the column for rainfall at Punta Arenas, snow has not been taken into account.

[22] The recent untimely death of this valuable official is deplored by all classes in Chili.

[23] This is doubtless the summit described by Darwin under the name Campana de Quillota. He gives the height as 6400 feet above sea-level. The figures in the text are taken from the Chilian survey.

[24] The mapping of the Andean chain is a task of immense difficulty, and although the Chilian survey is the best that has yet been executed, it leaves much to be desired. Even in the small district which I was able to visit, I found several grave errors in Petermann’s map, reduced from the Chilian survey, which is, nevertheless, the best that has been published in Europe. One of the most serious is the omission of the Uspallata Pass, the most frequented of those leading from Central Chili to the Argentine territory, which is neither named nor correctly indicated by the tints adopted to mark the zones of elevation.

[25] “Origin of Species,” 3rd edit., p. 410.

[26] Molina, one of the most pernicious blunderers who have brought confusion into natural history, grouped together under the generic name _Peumus_ several Chilian plants having no natural connection with each other. Misled by his erroneous description, botanists have applied the name _peumus_ to a fragrant shrub, common about Valparaiso and elsewhere, which is known in the country by the name _boldu_.

[27] The Baths of Cauquenes are said to be 2523 feet above the sea; the _Morro_, by aneroid observation, is about 2000 feet higher.

[28] As happens with many other plants described by early botanists, there has been much confusion in regard to the species named by Linnæus _Lobelia Tupa_. The plant was first made known to Europeans by the excellent traveller, Father Feuillée, whose “Journal des Observations Physiques Mathématiques et Botaniques faites sur les côtes de l’Amérique meridionale, etc.,” published in 1714, is a book which may still be consulted with advantage. His descriptions of plants are usually careful and accurate, but the accompanying plates all ill-executed and often misleading. Linnæus, followed by Willdenow, refers to Feuillée’s work, but gives a very brief descriptive phrase which suits equally well Feuillée’s plant and several others subsequently discovered. Aiton, in the “Hortus Kewensis,” gives the name _Lobelia Tupa_ to a plant which is plentiful about Valparaiso, where I found it still in flower, the seeds of which were received at Kew about a century ago from Menzies. This is now generally known by the not very appropriate name _Tupa salicifolia_ of Don, but was first published by Sims in the _Botanical Magazine_, No. 1325, as _Lobelia gigantea_, which name it should now bear. The plant which I found near Cauquenes appears to be the _Tupa Berterii_ of Decaudolle, a rare species, apparently not known to the authors of the “Flora Chilena.” No doubt could have arisen as to the plant intended by Linnæus as _Lobelia Tupa_ if writers had referred to Feuillée’s full and accurate description. His account of the poisonous effects of the plant was probably derived from the Indians, and may be exaggerated. The whole plant, he says, is most poisonous, the mere smell causing vomiting, and any one touching his eyes after handling the leaves is seized with blindness. I may remark that the latter statement, which appears highly improbable, receives some confirmation from the observations of Mr. Nation, mentioned above in page 77. The plant which I saw in Peru, but failed to collect, is much smaller than most of the Chilian species, and has purple flowers, but is nearly allied in structure. It is probably the _Tupa secunda_ of Don. I gather from a passage in one of Mr. Philippi’s writings that the word _tupa_ in Araucanian signifies poison. We are yet, I believe, ignorant of the chemical nature of the poisonous principle contained in the plants of this group.

[29] The measurements of the height of the peak of Aconcagua vary considerably in amount, but I believe that the most reliable is that adopted by Petermann--6834 metres, or 22,422 English feet.

[30] The inconvenience of using a periphrasis for the name of so important a country may warrant my adoption of the obvious name Argentaria in place of Argentine territory, or Argentine Confederation, and I shall adhere to the shorter designation in the following pages.

[31] It is quite possible that the bird which I took for the black albatross was the giant petrel, common, according to Darwin, in these waters, and closely resembling an albatross.

[32] See an interesting paper in the _Journal of Botany_ for July, 1884.

[33] The estimates given by Pissis do not rest on accurate observations, and seem to me exaggerated. I should be inclined to reckon the difference of height of the snow-line between the extreme stations as nearer to two thousand than to three thousand feet.

[34] I am not aware that the concurrent conclusions as to the height of this mountain have been verified by accurate observations, but the height commonly given appears to be a close approximation to the truth.

[35] “Flora Antarctica,” vol. ii. p. 289.

[36] See Appendix B.

[37] It is unfortunate that the Spaniards who had the naming of so large a part of the American continent should have shown so little inventive faculty. When they did not adopt a native name for a river, they rarely got beyond Red River, Black River, or Big River, and wherever we turn we encounter a Rio Colorado, a Rio Negro, or a Rio Grande.

[38] The constant inconvenience of employing such cumbrous expressions as Argentine Confederation or Argentine territory for a state of such vast extent and such yearly increasing importance must be felt by every one who has occasion to speak or write about this region of America. I trust that I shall be forgiven if in this book, as well as elsewhere, I have taken the liberty of applying a single name, which has nothing about it so strange as that it should not long since have come into use.

[39] The Paranà, with its great tributary the Paraguay, drains an area of more than 1,100,000 square miles; the basin of the Uruguay is reckoned at 153,000 square miles.

[40] The term _provinces_, commonly applied to the federated States, is misleading, and should be laid aside.

[41] Much information respecting this country is to be found in a volume entitled, “The Argentine Republic,” published in 1876 for the Centenary Exhibition at Philadelphia. It contains a series of papers prepared by Mr. Richard Napp, assisted by several German men of science.

[42] Dr. Hann (“Klimatologie,” p. 657, _et seq._) has discussed the causes of the prevalent high barometric pressure on both coasts of temperate South America, and has shown that in winter the area of maximum pressure moves northward towards the Tropic of Capricorn.

[43] The species common here is allied to _T. stricta_, but is not, I think, identical.

[44] The best general account of the geology of Brazil that I have seen is contained in a short paper by Orville A. Derby, entitled, “Physical Geography and Geology of Brazil.” It was published in the _Rio News_, in December, 1884, and, through the kindness of Mr. Geikie, i have seen a reprint in the library of the School of Mines.

[45] _Proceedings of the Royal Geographical Society_ for 1879, p. 564.

[46] See his valuable work, “Climats, Géologie, Faune et Géographie Botanique du Bresil.”

[47] “Klimatologie,” p. 382.

[48] Darwin’s estimate of the height was one thousand feet, while Professor Moseley gives double that amount. I incline to think that the lower figure is nearer to the truth.

[49] I borrow this statement from the excellent “Lehrbuch der Klimatologie,” by Dr. Julius Hann. Stuttgart, 1883.

[50] See _Reports of the British Association for the Advancement of Science_ for 1882, pp. 451-453.

[51] It is remarkable that there is no reference to the investigations of M. de St. Robert, and the formula deduced from them, in the article on the “Barometrical Measurement of Heights,” in the new edition of the _Encyclopædia Britannica_.

[52] Published by the War Department, United States Army, _Professional Papers of the Signal Service_, No. xv.

[53] Air nearly saturated with vapour is lighter than air relatively dry; and hence it may happen that, when a current of moist air meets one relatively dry, it will flow over the latter if they are nearly at the same temperature, but if the drier current be much warmer, it may flow beneath it.

[54] On this subject see _Handbuch der Klimatologie_, by Julius Hann, pp. 141, _et seq._ See also Tables I. and II. in a report on thermometric observations in the Alps, by J. Ball, in _Reports of the British Association for the Advancement of Science_ for 1862, pp. 366-368.

[55] See “Die Barometrischen Höhenmessungen und ihre Bedeutung für die Physik der Atmosphäre,” Leipzig, 1870, by R. Rühlmann.

[56] I use the term “eccentricity” in the popular sense, to express the distance of the focus from the centre of the ellipse.

[57] Viewed in the light of Mr. Langley’s recent researches on solar radiation, all these numerical determinations are probably far from the truth; but the errors do not much affect the present argument.

[58] The observations at Stanley Harbour, which are those adopted by Dr. Hann (_Klimatologie_, p. 697), show temperatures notably lower than those recorded for a place in the islands lying farther south, which are given in the _Zeitschrift der Œsterreichischen Gesellschaft für Meteorologie_, vol. v. p. 369. The mean of the two is probably nearly correct.

[59] These figures are derived from the tables given in the _Anales de la Oficina Meteorologica Argentina_, by B. Gould, vol. iii. The figures show a considerable amount of annual variation. The monthly means of the six months from February to July, 1879, exceed those of the same period in 1878 by more than 2° Fahr.

Transcriber’s Notes

Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in this book; otherwise they were not changed.

Simple typographical errors were corrected; occasional unbalanced quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

Index not checked for proper alphabetization or correct page references.

Page 4: “30·40” was misprinted as “39·40”.