Chapter V: Part 5

The great coolness, I might almost say cold, which prevails for a considerable part of the year within the tropics on the coast of Peru, causing the thermometer to sink to 12° Reaumur (59° Fahrenheit), is, as I have noticed elsewhere, by no means to be ascribed to the vicinity of the snow-covered Andes, but rather to the fogs (garua) which veil the solar disk, and to a _cold sea current_ which, commencing in the antarctic regions and coming from the south-west, strikes the coast of Chili near Valdivia and Conçeption, and thence streams rapidly along the coast to the northward, as far as Cape Pariña. On the coast, near Lima, the temperature of the Pacific is 12°.5 Reaumur (60°.2 Fahr.), whilst in the same latitude out of the current it is 21° R. (79°.2 Fahr.) It is singular that so striking a fact should have remained unnoticed until my visit to the shores of the Pacific, in October 1802.

The variations of temperature of different regions depend in a great degree on the character of the bottom of the “aerial ocean,” or on the nature of the floor or base, whether land or sea, continental or oceanic, on which the atmosphere rests. Seas, often traversed by currents of warmer or colder water, (oceanic rivers), have an effect very different from that of continental masses, whether unbroken or articulated, or of islands, which latter may be regarded as shallows in the aerial ocean, and which, notwithstanding their small dimensions, exert, often to a great distance, a notable influence on the climate of the sea. In continental masses we must distinguish between sandy deserts devoid of vegetation, savannahs or grassy plains, and forest-covered districts. In Upper Egypt and in South America, Nouet in the former, and myself in the latter, found respectively at noon the temperature of the ground composed of granitic sand 54°.2 and 48°.4 Reaumur (154° and 141° Fahr.) Many careful observations in Paris have given, according to Arago, 40° and 42° Reaumur, 122° and 126°.5 Fahrenheit. (Asie Centrale, T. iii. p. 176.) The Savannahs, which between the Missouri and the Mississipi are called Prairies, and which appear in South America as the Llanos of Venezuela and the Pampas of Buenos Ayres, are covered with small monocotyledonous plants of the family of Cyperaceæ, and with grasses of which the thin pointed stalks or ears, and the delicate lanceolate leaves or blades, radiate towards the unclouded sky, and possess an extraordinary power of “emission.” Wells and Daniell (Meteor. Essays, 1827, p. 230 and 278) have even seen in our latitude, where the atmosphere has so much less transparency, the thermometer sink 6°.5 or 8° of Reaumur (14°.5 or 18° Fahrenheit), on being placed on the grass. Melloni, in a memoir, “Sull abassamento di temperatura durante le notti placide e serene,” 1847, p. 47 and 53, has shewn how in a calm state of the atmosphere, which is a necessary condition of strong radiation and of the formation of dew, the cooling of the grassy surface is also promoted by the particles of air which are already cooled sinking to the ground as being the heaviest. In the vicinity of the equator, under the clouded sky of the Upper Orinoco, the Rio Negro, and the Amazons River, the plains are clothed with dense primeval forests; but to the north and south of this wooded region there extend from the zone of palms and lofty dicotyledonous trees, in the northern hemisphere, the Llanos of the Lower Orinoco the Meta and the Guaviare, and in the southern hemisphere the Pampas of the Rio de la Plata and of Patagonia. The space thus occupied by Savannahs or grassy plains in South America is at least nine times as great as the area of France.

The wooded region acts in a threefold manner in diminishing the temperature by cooling shade, by evaporation, and by radiation. Forests,--which in our temperate zone consist of trees living together in “society,” _i. e._, many individuals of one, or of a few kinds, of the families of Coniferæ or Amentaceæ, oaks, beeches, and birches, but in the tropics, of an immense variety of trees living separately or “unsocially,”--protect the ground from the direct rays of the sun, evaporate fluids elaborated by the trees themselves, and cool the strata of air in immediate contact with them by the radiation of heat from their appendicular organs or leaves. The latter are far from being all parallel with each other; they are, on the contrary, variously inclined to the horizon, and, according to the law developed by Leslie and Fourier, the influence of this inclination upon the quantity of heat emitted by radiation is such, that the power of radiation (pouvoir rayonnant) of a measured surface _a_, having a given oblique direction, is equal to the “pouvoir rayonnant” which would belong to a surface of the size of _a_, projected on a horizontal plane. Now in the initial condition of radiation, of all the leaves which form the summit of a tree and partly cover each other, those are first cooled which are directed without any intervening screen towards the unclouded sky. The cooling result (or the exhaustion of heat by emission) will be the more considerable the greater the thinness of the leaves. A second stratum of leaves has its upper surface turned to the under surface of the first stratum, and will give out more heat by radiation towards that stratum than it can receive by radiation from it. The result of this unequal exchange will thus be a loss of temperature for the second stratum of leaves also. A similar operation will continue from stratum to stratum until all the leaves of the tree, by greater or less radiation as modified by their diversity of position, have passed into a state of stable equilibrium of which the law can be deduced by mathematical analysis. In this manner, in the long and clear nights of the equinoctial zone, the forest air contained in the intervals between the strata of leaves becomes cooled by the process of radiation; and by reason of the great quantity of its thin appendicular organs or leaves, a tree, the horizontal section of whose summit would measure for example 2000 square feet, would act in diminishing the temperature of the air equivalently to a space of bare or turf-covered ground several thousand times greater than 2000 square feet (Asie Centrale, T. iii. p. 195-205). I have sought thus to develop in detail the complicated effects which make up the total action of extensive forests upon the atmosphere, because they have been so often touched upon in reference to the important question concerning the climates of ancient Germany and Gaul.

As in the old continent European civilization has had its principal seats on a western coast, it could not but be early remarked that, under equal degrees of latitude, the opposite eastern coast of the United States was several degrees colder in mean annual temperature than Europe, which is, as it were, a projecting western peninsula to Asia, as Brittany is to the rest of France. But in this remark it was forgotten that these differences decrease from the higher to the lower latitudes in such manner that they almost entirely disappear from 30° downwards. For the west coast of the new continent, exact thermometric observations are still almost entirely wanting; but the mildness of the winters in New California shews that the west coasts of America and Europe, under the same parallels of latitude, probably differ little from each other in mean annual temperature. The subjoined table shows what are the corresponding mean annual temperatures, in the same geographical latitudes, of the west coast of Europe and the east coast of the New Continent.

+---------+------------+----------+------------------------+-----------------------+
| | | | Reaumur. | Fahrenheit. |
| | | +------------+-----------+-----------+-----------+
|Similar | East Coast |West Coast|Mean |Differences|Mean |Differences|
|degrees | of |of |temperature |of annual |temperature|of annual |
|of | America. |Europe. |of the year,|temperature|of the |temperature|
|latitude.| | |of winter, |of East |year, of |of East |
| | | |and of |coast of |winter, and|coast of |
| | | |summer. |America |of summer. |America |
| | | | |and West | |and West |
| | | | |coast of | |coast of |
| | | | |Europe. | |Europe. |
+---------+------------+----------+------------+-----------+-----------+-----------+
| | | | -14°.4 | | -0°.5 | |
|57° 10′ | Nain | | -2°.8 ----- | | 25°.8 ----- | |
| | | | 6°.1 | | 45°.8 | |
| | | | | 9°.2 | | 20°.7 |
| | | | -0°.2 | | -31°.5 | |
|57° 41′ | |Gottenburg| 6°.4 ----- | | 46°.4 ----- | |
| | | | 13°.5 | | 62°.4 | |
+---------+------------+----------+------------------------+-----------------------+
+---------+------------+----------+------------------------+-----------------------+
| | | | -4°.0 | | 23°.0 | |
|47° 34′ | St. John’s | | 2°.7 ----- | | 38°.0 ----- | |
| | | | 9°.8 | | 54°.0 | |
| | | | | | | |
| | | | -0°.4 | | 31°.0 | |
|47° 30′ | |Ofen | 8°.2 ----- | 5°.8 | 50°.5 ----- |13°.0 |
| | |(or Buda) | 16°.8 | | 69°.8 | |
| | | | | | | |
| | | | 2°.6 | | 37°.8 | |
|48° 50′ | |Paris | 8°.7 ----- | | 51°.6 ----- | |
| | | | 14°.5 | | 64°.6 | |
+---------+------------+----------+------------------------+-----------------------+
+---------+------------+----------+------------------------+-----------------------+
| | | | -3°.5 | | 24°.2 | |
|44° 39′ |Halifax | | 5°.1 ----- | | 43°.5 ----- | |
| | | | 13°.8 | | 63°.0 | |
| | | | | 6°.1 | | 13°.7|
| | | | 4°.8 | | 42°.8 | |
|44° 50′ | |Bordeaux | 11°.2 ----- | | 57°.2 ----- | |
| | | | 17°.4 | | 71°.2 | |
+---------+------------+----------+------------------------+-----------------------+
+---------+------------+----------+------------------------+-----------------------+
| | | | 0°.1 | | 32°.2 | |
|40° 43′ |New York | | 9°.1 ----- | | 52°.5 ----- | |
| | | | 18°.2 | | 73°.0 | |
| | | | | | | |
| | | | 0°.1 | | 32°.2 | |
|39° 57′ |Philadelphia| | 9°.0 ----- | | 52°.2 ----- | |
| | | | 18°.1 | | 72°.8 | |
| | | | | | | |
| | | | 1°.8 | | 36°.0 | |
|38° 53′ |Washington | | 10°.2 ----- | 3°.4 | 55°.0 ----- | 8.0 |
| | | | 17°.4 | | 71°.2 | |
| | | | | | | |
| | | | 7°.8 | | 49°.5 | |
|40° 51′ | |Naples | 12°.9 ----- | | 61°.0 ----- | |
| | | | 19°.1 | | 75°.0 | |
| | | | | | | |
| | | | 9°.0 | | 52°.2 | |
|38° 52′ | |Lisbon | 13°.1 ----- | | 61°.5 ----- | |
| | | | 17°.4 | | 71°.2 | |
+---------+------------+----------+------------------------+-----------------------+
+---------+------------+----------+------------------------+-----------------------+
| | | | 12°.2 | | 59°.5 | |
|29° 48′ |St. Augustin| | 17°.9 ----- | | 72°.2 ----- | |
| | | | 22°.0 | | 81°.5 | |
| | | | | 0.2 | | 0°.4 |
| | | | 11°.8 | | 58°.5 | |
|30° 2′ | |Cairo | 17°.7 ----- | | 71°.8 ----- | |
| | | | 23°.4 | | 84°.7 | |
+---------+------------+----------+------------------------+-----------------------+

In the column of temperatures in the preceding table the first number represents the temperature of the year; that which stands in place of a numerator the mean winter temperature; and that which stands in the place of a denominator the mean summer temperature. Besides the great difference of mean annual temperature, there is also a striking difference between the two coasts in respect to the distribution of that temperature into the different seasons of the year, and it is this distribution which is most influential both on our feelings and on the processes of vegetation. Dove remarks generally, that the summer temperature of America is lower under equal degrees of latitude than that of Europe: (Temperatur tafeln nebst Bemerkungen über die Verbreitung der Wärme auf der Oberfläche der Erde, 1848, S. 95.) The climate of St. Petersburgh, (or to speak more correctly the mean annual temperature of that city which is in lat. 59° 56′), is found on the east coast of America in lat. 47-1/2°, or 12-1/2° more to the south; in like manner we find the climate of Konigsberg, (lat. 54° 43′), at Halifax, (lat. 44° 39′). The temperature of Toulouse, (lat. 43° 36′) corresponds to that of Washington (lat. 38° 53′).

It would be very hazardous to lay down any general statements respecting the temperature in the territory of the United States of America, as we must distinguish in that territory three regions:--1, the Atlantic States east of the Alleghanies; 2, the Western States in the wide basin between the Alleghanies and the Rocky Mountains, through which flow the Mississipi, the Ohio, the Arkansas, and the Missouri; 3, the high plains between the Rocky Mountains, and the Maritime Alps of New California through which the Oregon or Columbia River finds a passage. Since the highly honourable establishment, by John Calhoun, of uninterrupted observations of temperature, made on an uniform plan at 35 military posts, and reduced to daily, monthly, and annual means, we have arrived at more just climatic views than those which were so generally received in the time of Jefferson, Barton, and Volney. These meteorological stations or observatories extend from the point of Florida and Thompson’s Island, (Key West), lat. 24° 33′, to the Council Bluffs on the Missouri; and if we reckon amongst them Fort Vancouver, lat. 45° 37′, they include differences of longitude of 40°.

It cannot be affirmed that, on the whole, the mean annual temperature of the second or middle region is higher than that of the first or Atlantic region. The further advance of certain plants towards the north, on the west of the Alleghany mountains, depends partly on the nature of those plants, and partly on the different distribution of the same annual quantity of heat. The wide valley of the Mississipi enjoys at its northern and southern extremities the warming influence of the Canadian Lakes, and of the Mexican Gulf stream. The five lakes, (Superior, Michigan, Huron, Erie, and Ontario), occupy a space of 92,000 English square miles. The climate is much milder and more equable in the neighbourhood of the lakes; for example, at Niagara, (lat. 43° 15′), the mean winter temperature is only half a degree of Reaumur (1°.2 Fahrenheit) below the freezing point, while at a distance from the lakes, in lat. 44° 53′, at the confluence of the river St. Peter’s with the Mississipi, the mean winter temperature of Fort Snelling is -7°.2 Reaumur, or 15°.9 Fahrenheit (see Samuel Forry’s excellent Memoir on “the Climate of the United States,” 1842, p. 37, 39, and 102.) At this distance from the Canadian Lakes, (whose surface is from 500 to 600--530 to 640 English--feet above the level of the sea, whilst the bottom of the lakes Michigan and Huron is about five hundred feet below it), recent observations have shewn the climate of the country to possess a proper continental character, _i. e._, hotter summers and colder winters. “It is proved,” says Forry, “by our thermometrical data, that the climate west of the Alleghany Chain is more excessive than that of the Atlantic side.” At Fort Gibson, on the Arkansas River which falls into the Mississipi in lat. 35° 47′, with a mean annual temperature hardly equal to that of Gibraltar, the thermometer in the shade, and without any reflected heat from the ground, has been seen, in August 1834, to rise to 37°.7 Reaumur, or 117° Fahrenheit.

The statement so often repeated, although unsupported by any thermometric measurements, that since the first European settlements in New England, Pennsylvania, and Virginia, the eradication of many forests on both sides of the Alleghanies had rendered the climate more equable, (_i. e._, milder in winter and cooler in summer), is now generally doubted or disbelieved. Series of trustworthy thermometric observations in the United States hardly extend so far back as 78 years. We see in the Philadelphia observations, that from 1771 to 1824, the mean annual temperature has hardly increased 1°.2 Reaumur, (or 2°.8 Fahrenheit),--a difference which is attributed to the increased size of the town, to its greater population, and to the numerous steam-engines. The difference may possibly be merely accidental, for I find in the same period an increase of mean winter cold, amounting to 0°.9 Reaumur, or 2° Fahrenheit; the three other seasons had become somewhat warmer. Three-and-thirty years’ observations at Salem in Massachusetts shew no alteration at all: the annual means oscillate, within a degree of Fahrenheit, about the mean of the whole number of years; and the winters of Salem, instead of having become milder, as supposed from the destruction of the forests in the course of the thirty-three years, have become colder by 1°.8 Reaumur, or 4° Fahrenheit. (Forry, p. 97, 101, and 107.)

As the east coast of the United States is comparable in respect to mean annual temperature in equal latitudes to the Siberian and Chinese coasts of the old continent, so also the west coasts of Europe and America have been very properly compared together. I will only take a few examples from the western region on the shores of the Pacific, for two of which (Sitka in Russian America, and Fort George, in the same latitudes respectively as Gottenburg and Geneva) I am indebted to Admiral Lütke’s voyage of circumnavigation. Iluluk and Danzig are nearly on the same parallel, and although the mean temperature of Iluluk, owing to its insular climate and to a cold sea-current, is somewhat lower than that of Danzig, yet the winter temperature of the American station is milder than that of the port on the Baltic.

+-----------+---------+------------------+-------------+-------------+
| |Latitude.| Longitude. | Reaumur. | Fahrenheit.|
| +---------+------------------+-------------+-------------+
| | | | 0°.6 | 33°.4|
|Sitka | 57° 3′ | 135° 16′ W. |5°.6 ----- | 44°.5 -----|
| | | | 10°.2 | 55°.0|
| | | | | |
| | | | -0°.2 | 31°.5|
|Gottenburg | 57° 41′ | 11° 59′ E. |6°.4 ----- | 46°.4 -----|
| | | | 13°.5 | 62°.4|
| | | | | |
| | | | 2°.6 | 37°.9|
|Fort George| 46° 18′ | 122° 58′ W. |8°.1 ----- | 50°.3 -----|
| | | | 12°.4 | 60°.0|
| | | | | |
| | | | 0°.7 | 33°.6|
|Geneva | 46° 12′ |(Alt. 1298 E. ft.)|7°.9 ----- | 49°.8 -----|
| | | | 14°.0 | 63°.5|
| | | | | |
| | | | -3°.1 | 25°.0|
|Kherson | 46° 38′ | 32° 39′ E. |9°.4 ----- | 53°.2 -----|
| | | | 17°.3 | 71°.0|
+-----------+---------+------------------+-------------+-------------+

Snow is hardly ever seen on the banks of the Oregon or Columbia river, and ice on the river lasts only a very few days. The lowest temperature which Mr. Ball once observed there in the winter of 1833 was 6-1/2° of Reaumur below the freezing point, or 17.4° Fahrenheit (Message from the President of the United States to Congress, 1844, p. 160; and Forry, Clim. of the U. States, p. 49, 67, and 73). A cursory glance at the summer and winter temperatures above given, shews that on and near the west coast, a true insular climate prevails. The winter cold is less than in the western parts of the old continent, and the summers are much cooler. The most striking contrast is presented by comparing the mouth of the Oregon with Forts Snelling and Howard, and the Council Bluffs, in the interior of the Mississipi and Missouri basin (Lat. 44°-46°),--where, to speak in the language of Buffon, we find an _excessive_, or true _continental_ climate,--a winter cold, on single days, of -28°.4 and -30°.6 Reaumur (-32° and -37° Fahr.), followed by mean summer temperatures of 16°.8 and 17°.5 Reaumur (69° and 71°.4 Fahr.)

[19] p. 10.--“_As if America had emerged later from the chaotic watery covering._”

An acute enquirer into nature, Benjamin Smith Barton, said long since with great truth, (Fragments of the Natural History of Pennsylvania, P. i. p. 4), “I cannot but deem it a puerile supposition, unsupported by the evidence of nature, that a great part of America has probably later emerged from the bosom of the ocean than the other continents.” The same subject was touched on by myself in a memoir on the primitive nations of America (Neue Berlinische Monatschrift, Bd. xv. 1806, S. 190). “Writers generally and justly praised have repeated but too often that America is in every sense of the word a New Continent. Her luxuriance of vegetation, the abundant waters of her enormous rivers, the unrepose of her powerful volcanoes, all (say they) proclaim that the still trembling earth, from the face of which the waters have not yet dried off, is here nearer to the chaotic primordial state than in the Old Continent. Such ideas appeared to me, long before I commenced my travels, alike unphilosophical and contrary to generally acknowledged physical laws. Fantastic images of terrestrial youth, and unrepose associated on the one hand,--and on the other, those of increasing dryness, and inertia in maturer age,--could only have presented themselves to minds more inclined to draw ingenious or striking contrasts between the two hemispheres, than to strive to comprehend, in one general view, the construction of the entire globe. Are we to regard the south of Italy as more modern than its northern portions, because the former is almost incessantly disquieted by earthquakes and volcanic eruptions? Besides, what small phenomena are the volcanoes and earthquakes of the present day, in comparison with those revolutions of nature which the geologist must suppose to have accompanied, in the chaotic state of the earth, the elevation, solidification, disruptions, and cleavings of the mountain masses? Diversity of causes must produce diversity in the operations of natural forces, in countries remote as well as near. Perhaps the volcanoes of the new continent, (of which I still reckon above 28 in a state of activity), have only continued to burn longer than others, because the lofty mountain ridges, on which they have broken forth in rows or series above long subterranean fissures, are nearer to the sea, and because this proximity seems, with a few exceptions, to affect the energy of the subterranean fires in some way not yet sufficiently explained. Besides, both earthquakes and fire-emitting mountains have periods of activity alternating with periods of repose. At the present moment,” (I wrote thus 42 years ago!) “physical disquiet and political calm reign in the New Continent, while in the Old the desolating strife of nations disturbs the enjoyment of the repose of nature. Perhaps a time is coming when, in this singular contrast between physical and moral forces, the two sides of the Atlantic will change parts. Volcanoes are quiescent for centuries before they burst forth anew; and the idea that in the so-called older countries, a certain peace must prevail in nature, is founded on a mere play of the imagination. There exists no reason for assuming one entire side of our planet to be older or newer than the other. Islands are indeed raised from the bed of the ocean by volcanic action, and gradually heightened by coral animals, as the Azores and many low flat islands of the Pacific; and these may indeed be said to be newer than many Plutonic formations of the European central chain. A small district of the earth, surrounded, like Bohemia and Kashmeer, (and like many of the vallies in the Moon), by annular mountains, may, by partial inundations, be long covered with water; and after the flowing off of this lake or inland sea, the ground on which vegetation begins gradually to establish itself might be said, figuratively, to be of recent origin. Islands have become connected with each other by the elevation of fresh masses of land; and parts of the previously dry land have been submerged by the subsidence of the oscillating ground; but submersions so general as to embrace a hemisphere, can, from hydrostatic laws, only be imagined as extending at the same time over all parts of the earth. The sea cannot permanently overflow the boundless plains of the Orinoco and the Amazons, without also overwhelming the plains adjoining the Baltic. The sequence and identity of the sedimentary strata, and of the organic remains of plants and animals belonging to the ancient world enclosed in those strata, shew that several great depositions have taken place almost simultaneously over the entire globe.” (For the fossil vegetable remains in the coal formation in North America and in Europe, compare Adolph Brongniart, Prodrome d’une Hist. des Végétaux Fossiles, p. 179; and Charles Lyell’s Travels in North America, vol. ii. p. 20).

[20] p. 10.--“_The Southern Hemisphere is cooler and moister than our Northern half of the globe._”

Chili, Buenos Ayres, and the southern parts of Brazil and Peru, have all, as a result of the narrowness of the continent of South America as it tapers towards the south, a true “insular climate;” or a climate of cool summers and mild winters. As far as the 48th or 50th parallel of latitude this character of the Southern Hemisphere may be regarded as an advantage, but farther on towards the Antarctic Pole, South America gradually becomes an inhospitable wilderness. The difference of latitude of the southern terminating points of Australia, (including Van Diemen Island), of Africa, and of America,--gives to each of these continents a peculiar character. The Straits of Magellan are between the 53d and 54th degrees of latitude, and yet in December and January, when the sun is 18 hours above the horizon, the temperature sinks to 4° Reaumur, or 41° Fahrenheit. Snow falls almost daily, and the highest atmospheric temperature observed by Churruca (1788) in December, (the summer of those regions), was not above 9° R., or 52°.2 Fahr. The Cabo Pilar, whose towering rock, though only 218 toises, or 1394 English feet high, may be regarded as the southern termination of the chain of the Andes, is almost in the same latitude as Berlin. (Relacion del Viage al Estrecho de Magallanes, apendice, 1793, p. 76.)

While in the Northern Hemisphere all the continents attain a sort of mean limit towards the Pole, coinciding pretty regularly with the parallel of 70° the terminating points in the Southern Hemisphere,--of America, in the deeply indented and intersected Tierra del Fuego,--of Australia,--and of Africa,--are respectively 34°, 46-1/2°, and 56° distant from the south pole. The temperature of the very unequal extents of ocean, which divide these southern points from the icy pole, contributes very materially to modify their climates. The areas of dry land in the Northern and Southern Hemispheres are to each other in the proportion of 3 to 1. But this inferiority in extent of continental masses in the Southern Hemisphere, as compared with the Northern, belongs much more to the temperate than to the torrid zone. In the temperate zones of the Northern and Southern Hemispheres, the ratio is as 13 to 1; in the torrid zones as 5 to 4. The great inequality in the distribution of the dry land exercises a very sensible influence on the strength of the ascending aerial current which turns towards the southern pole, and on the temperature of the Southern Hemisphere. Some of the noblest forms of tropical vegetation, for example the tree-ferns, advance south of the equator as far as the parallels of 46°, and of even 53°; whereas north of the equator they are not found beyond the tropic of Cancer. (Robert Brown, Appendix to Flinders’ Voyage, p. 575 and 584; Humboldt, de distributione geographica Plantarum, p. 81-85.) Tree-ferns thrive extremely well at Hobart Town in Van Diemen Island, (lat. 42° 53′), where the mean annual temperature is 9° Reaumur, or 52°.2 Fahrenheit, and is therefore 1°.6 Reaumur, or 3°.6 Fahrenheit, less than that of Toulon. Rome is almost a degree of latitude farther from the equator than Hobart Town, and has an annual temperature of 12°.3 R., or 59°.8 Fahr.;--a winter temperature of 6°.5 R., or 46°.4 Fahr.,--and a summer temperature of 24° R., or 86° Fahr.; these three values being in Hobart Town 8°.9, 4°.5, and 13°.8 R., or 52°.0, 42°.2, and 63°.0 Fahr. In Dusky Bay, New Zealand, tree-ferns grow in S. lat. 46° 8′, and in the Auckland and Campbell Islands, even in 53° S. lat. (Jos. Hooker, Flora Antarctica, 1844, p. 107.)

In the Archipelago of Tierra del Fuego,--where, in the same latitude as Dublin, the mean winter temperature is 0°.4 Reaumur, (33° Fah.) and the mean summer temperature only 8° R., or 50° Fahr.,--Captain King found the “vegetation thriving most luxuriantly in large woody-stemmed trees of Fuchsia and Veronica”; while this vigour of vegetation, which, especially on the western coast of America in 38° and 40° of south latitude, is so picturesquely described by Charles Darwin, suddenly disappears south of Cape Horn, on the rocks of the Southern Orkney and Shetland Islands, and of the Sandwich Archipelago. These Islands, but scantily covered with grass, moss, and lichens, “Terres de Désolation,” as the French navigators call them, are still far north of the Antarctic Circle; whereas in the Northern Hemisphere in 70° of latitude, at the extremity of Scandinavia, fir-trees attain a height of between 60 and 70 English feet. (Compare Darwin in the “Journal of Researches,” 1845, p. 244, with King in vol. i. of the Narrative of the Voyages of the Adventure and Beagle, p. 577.) If we compare Tierra del Fuego, and particularly Port Famine in the Straits of Magellan in lat. 53° 38′, with Berlin, which is one degree nearer the equator, we find for

Berlin 6°.8, -0°.5/13°.9 R., 47°.2, 30°.8/63°.2 Fahr.; and for

Port Famine 4°.7, 1°.2/8°.0 R., 42°.6, 34°.8/50°.0 Fahr.

I subjoin in one view the few well-assured temperature data which we at present possess, for the lands of the temperate zone in the Southern Hemisphere, and which may be compared with the temperatures of the Northern Hemisphere, in most parts of which the distribution into summer heat and winter cold is so different and so much less equable. I employ the convenient method of notation before used and explained in pages 129-131.

+---------------------+---------+------------------------------+
| | | Mean Annual, Winter, |
| Place. | South | and Summer Temperature. |
| | |---------------+--------------+
| |Latitude.| Reaumur.| Fahrenheit.|
+---------------------+---------+---------------+--------------+
|Sidney and Paramatta | | 10°.0 | 54°.5 |
| (New Holland.) | 33°.50′ |14°.5 ----- |64°.5 ----- |
| | | 20°.2 | 77°.5 |
| | | | |
| | | 11°.8 | 58°.5 |
|Cape Town (Africa.) | 33°.55′ |15°.0 ----- |65°.7 ----- |
| | | 18°.3 | 73°.3 |
| | | | |
| | | 9°.1 | 52°.5 |
|Buenos Ayres | 34°.17′ |13°.5 ----- |62°.4 ----- |
| | | 18°.2 | 73°.0 |
| | | | |
| | | 11°.3 | 57°.3 |
|Monte Video | 34°.54′ |15°.5 -----(?)|66°.8 ----- |
| | | 20°.2 | 77°.5 |
| | | | |
|Hobart Town (Van | | 4°.5 | 42°.2 |
| Diemen Island.) | 42°.45′ | 9°.1 ----- |52°.5 ----- |
| | | 13°.8 | 63°.0 |
| | | | |
|Port Famine (Straits | | 1°.2 | 34°.8 |
| of Magellan.) | 53°.38′ | 4°.7 ----- |42°.6 ----- |
| | | 8°.0 | 50°.0 |
+---------------------+---------+---------------+--------------+

[21] p. 11.--“_A connected Sea of Sand._”

As the Heaths formed of socially growing Ericeæ, which stretch from the mouth of the Scheldt to that of the Elbe and from the point of Jutland to the Harz, may be regarded as one connected _tract of vegetation_,--so the seas of sand may be traced through Africa and Asia, from Cape Blanco to beyond the Indus, or through an extent of 5600 geographical miles. Herodotus’s Sandy Region interrupted by Oases, called by the Arabs the Desert of Sahara, traverses almost the whole of Africa, which it intersects like a dried-up arm of the sea. The valley of the Nile is the eastern limit of the Lybian Desert. Beyond the Isthmus of Suez, beyond the porphyritic, syenitic, and basaltic rocks of Sinai, begins the Desert mountain plateau of Nedjid, which occupies the whole of the interior of the Arabian Peninsula, and is bounded to the west and south by the fertile and happier coast lands of Hedjaz and Hadhramaut. The Euphrates bounds the Arabian and Syrian Deserts towards the east. Immense seas of sand, (bejaban), cross Persia from the Caspian to the Indian Sea. Among them are the salt and soda Deserts of Kerman, Seistan, Beloochistan, and Mekran. The latter is separated from the Desert of Moultan by the Indus.

[22] p. 11.--“_The western part of the Atlas._”

The question respecting the position of the ancient Atlas has been much discussed in modern times, but the oldest Phœnician legends have been confounded in this discussion with the later fables of the Greeks and the Romans. A man who combined deep philological with thorough mathematical and astronomical knowledge, Professor Ideler, (the father,) was the first person who explained and dispelled the confusion of ideas which had previously existed on this subject. I permit myself to introduce here the remarks that clear-sighted and highly-informed writer has communicated to me on this important subject.

“At a very early period of the world the Phœnicians ventured beyond the Straits of Gibraltar. They built Gades and Tartessus on the Spanish, and Lixus and several other towns on the Mauritanian coasts of the Atlantic. They sailed along those coasts northwards to the Cassiterides where they obtained tin, and to the Prussian coast from whence they brought amber; and southwards, past Madeira, to the Cape de Verde Islands. They visited, among other places, the Canaries, and were struck by the appearance of the lofty Peak of Teneriffe, enhanced by its rising immediately from the sea. Through the colonies which they sent to Greece, and especially through that which came under Cadmus to Bœotia, the notice of this mountain rising high above the region of clouds, and of the “Fortunate Islands,” adorned with fruits of every kind, and especially with the golden orange, spread into Greece. Here the tradition was propagated by the songs of the bards, and thus reached Homer. He speaks in the Odyssey (i. 52) of an “Atlas who knows all the depths of the sea, and who supports the great pillars which divide heaven and earth from each other.” He speaks, too, in the Iliad, of the Elysian fields, which he describes as a lovely land in the west. (Il. iv. 561.) Hesiod expresses himself in a similar manner respecting Atlas, who he makes a neighbour of the nymphs the daughters of Hesperus. (Theog. V. 517.) He calls the Elysian fields, which he places at the western limit of the earth, the islands of the Blest. (Op. et dies, v. 167.) Later poets have added further embellishments to these myths of Atlas, of the Hesperides, their golden apples, and the Islands of the Blest, assigned as the dwelling-place of the virtuous after death; and have combined with them the expeditions of the Tyrian god of trade, Melicertes (the Grecian Hercules).

“The Greeks only began at a very late date to rival the Phœnicians and Carthaginians in navigation. They visited the coasts of the Atlantic it is true, but never appear to have penetrated far into the ocean. I doubt whether they ever saw the Canaries and the Peak of Teneriffe. They believed that Atlas, which their poets and legends described as a very high mountain placed at the western limit of the earth, must be sought on the west coast of Africa. It was placed there also by their later geographers, Strabo, Ptolemy, and others. As there is not any single mountain distinguished by its elevation in north-western Africa, the true situation of Mount Atlas has been a subject of perplexity; and it has been sought, sometimes on the coast, sometimes in the interior, sometimes near the Mediterranean, and sometimes further towards the south. It became the custom (in the first century of our era, when the Roman arms penetrated into the interior of Mauritania and Numidia,) to give the name of Atlas to the African chain of mountains which runs from west to east almost parallel with the coast of the Mediterranean. Pliny and Solinus were, however, very sensible that the descriptions of Mount Atlas given by the Greek and Roman poets were not applicable to this long mountain chain; and they therefore thought it necessary to transfer the Atlas, of which they gave a picturesque description in accordance with the poetic legends, to the terra incognita of Central Africa. According to what has been said, the Atlas of Homer and Hesiod can only be the Peak of Teneriffe; and the Atlas of the Greek and Roman geographers must be in Northern Africa.”

I will only add the following remarks to this instructive discussion by Professor Ideler. According to Pliny and Solinus, Atlas rises from a sandy plain (e medio arenarum); and elephants (which certainly were never known in Teneriffe) feed on its declivity. What we now term Atlas is a long ridge. How came the Romans to recognise in this long ridge the isolated conical mountain of Herodotus? May not the reason be found in the optical delusion by which every mountain chain seen in profile, in the prolongation of its direction, has the appearance of a narrow cone? I have often seen in this manner, from the sea, the ends of long chains or ridges, which might be taken for isolated mountains. According to Höst the Atlas is covered near Morocco with perpetual snow, which implies an elevation of above 1800 toises, or 11510 English feet. It is also remarkable that, according to Pliny, the “Barbarians,” _i. e._ the ancient Mauritanians, called the Atlas “Dyris.” The chain of the Atlas is still called by the Arabs Daran, a word which has almost the same consonants as Dyris. Hornius, on the other hand (de Originibus Americanorum, p. 195), thinks that he recognises the word Dyris in the Guanche name of the Peak of Teneriffe, Aya-Dyrma. On the connection between purely mythical ideas and geographical traditions, and on the way in which the Titan Atlas gave occasion to the image of a mountain supporting the heavens, beyond the Pillars of Hercules, see Letronne’s “Essai sur les Idées cosmographiques qui se rattachent au nom d’Atlas,” in Férussac’s Bulletin universel des Sciences, Mars 1831, p. 10.

Considering that our present (it is true, very limited) geological knowledge of the mountainous parts of North Africa does not make us acquainted with any trace of volcanic eruptions within historic times, it is very remarkable to find among the ancients so many indications of a belief in the existence of this class of phenomena, in the Western Atlas, and in the neighbouring west coast of the continent. The streams of fire, so often mentioned in Hanno’s ship-journal, may indeed have only been strips of burning grass, or signal fires kindled by the wild inhabitants of the coasts to give to each other notice of the danger threatened by the appearance of the hostile vessels. The lofty flame-enlightened summit of the “chariot of the gods” (θεῶν ὅχημα), may recall obscurely the Peak of Teneriffe; but farther on Hanno describes a singular conformation of ground. He finds in the Gulf near the Western Horn, a large island, and in it a salt lake which again contains a smaller island. South of the bay of the Gorilla Apes, the same conformation is repeated. Is this a description of coral productions, of “lagoon islands, (Atolls)” or volcanic “crater lakes” in the middle of which a cone has been upheaved? The Triton lake was not in the neighbourhood of the lesser Syrtis, but near the Atlantic coast. (Asie Cent. T. i. p. 179.) The lake disappeared in consequence of earthquakes which were accompanied by great outbursts of fire. Diodorus (Lib. iii. 53, 55) says expressly, πυρὸς ἐκφυσήματα μεγάλα. But the most wonderful conformation is ascribed to the “hollow Atlas” in a passage hitherto little noticed, occurring in one of the philosophic Dialexes of Maximus Tyrius. This Platonic philosopher lived in Rome, under Commodus. The situation of his Atlas is “on the continent, where the Western Lybians inhabit a projecting peninsula. The mountain has in it towards the sea a semicircular deep abyss.” The precipices are so steep that they cannot be descended; the abyss below is filled with trees, and “one looks down upon their summits, and on the fruits which they bear, as if one was looking into a well.” (Maximus Tyrius, viii., 7, ed. Markland.) The description is so graphic and so individually marked, that it doubtless conveys the recollections impressed by a real prospect.

[23] p. 11.--“_The Mountains of the Moon, Djebel al Komr._”

The Mountains of the Moon of Ptolemy (Lib. iv. cap. 9,) (σελήνης ὅρος) form on our older maps an immense uninterrupted mountain zone, traversing Africa from east to west. The existence of these mountains appears certain; but their extent, their distance from the Equator, and their general direction, are all unsolved problems. I have already alluded in another work, (Cosmos, vol. ii. p. 191, and note 297, Engl. ed.) to the manner in which a closer acquaintance with Indian languages, and with the ancient Persian idiom, the Zend, teaches us that part of the geographical nomenclature of Ptolemy forms an historic monument of the commercial connection of the west with the most distant regions of Southern Asia and Eastern Africa. The same direction of ideas shews itself in a question very recently brought forward. It is asked, whether the great geographer and astronomer of Pelusium meant in the name of “Mountains of the Moon,” as in that of the “Island of Barley” (Jabadiu, Java), merely to give the Greek translation of a native name;--whether (as is most probable) El Istachri, Edrisi, Ibn-al-Vardi, and other early Arabian geographers, only transferred the nomenclature of Ptolemy into their own language;--or whether they were misled by similarity in the sound of the words and the manner of writing. In the notes to the translation of Abd-Allatif’s celebrated description of Egypt, my great instructor, Silvestre de Sacy, (éd. de 1810, p. 7 and 353,) says expressly: “On traduit ordinairement le nom de ces montagnes que Léon Africain regarde comme les sources du Nil, par _montagnes de la lune_, et j’ai suivi cet usage. Je ne sais si les Arabes ont pris originairement cette dénomination de Ptolémée. On peut croire qu’ils entendent effectivement aujourd’hui le mot قمر dans le sens de la _lune_ en le prononçant ‘Kamar’; je ne crois pas cependant que ç’ait été l’opinion des anciens écrivains arabes qui prononcent, comme le prouve Makrizi, Komr. Aboulféda rejette positivement l’opinion de ceux qui prononcent kamar, et qui dérivent ce nom de celui de la lune. Comme le mot komr, considéré comme pluriel de اقمر, signifie un objet d’une _couleur verdâtre_ ou d’un blanc sale, suivant l’auteur du Kamous, il paroit que quelques écrivains ont cru que cette montagne tiroit son nom de sa couleur.”

The learned Reinaud, in his recent excellent translation of Abulfeda (T. ii., P. i., p. 81-82), considers it probable that the Ptolemaic interpretation of the name, by “Mountains of the Moon” (ὅρη σεληναῖα), was that originally adopted by the Arabian writers. He remarks that in the Moschtarek of Yakut, and in Ibn-Said, the mountains are written al-Komr, and that Yakut writes in the same way the name of the island of Zendj (Zanguebar). The Abyssinian traveller Beke, in his learned critical memoir on the Nile and its tributaries (Journal of the Royal Geographical Society of London, vol. xvii. 1847, p. 74-76), seeks to prove that Ptolemy had merely formed his σελήνης ὅρος from a native name, for which he was indebted to intelligence received through the medium of the extensive commercial intercourse which prevailed. He says, “Ptolemy knew that the Nile rises in the mountainous country of Moezi; and in the languages which extend over a great portion of South Africa (for example, in the languages of Congo, Monjou, and Mozambique), the word Moezi signifies the moon. A great south-western country was called Mono-Muezi, or Mani-Moezi, _i. e._ the land of the king of Moezi (of the king of the Moon country), for in the same family of languages in which Moezi or Muezi signifies the Moon, Mono or Mani signifies a king. Alvarez, in the Viaggio nella Ethiopia (Ramusio, vol. i, p. 249,) speaks of the ‘regne di Manicongo,’ the kingdom of the king of Congo.” Beke’s opponent, Ayrton, seeks the origin of the White Nile (Bahr el Abiad), not as do Arnaud, Werne, and Beke, near the equator, or even south of it (and in 29° E. long. from Paris, or 31° 22′ from Greenwich), but with Antoine d’Abbadie far to the north-east, in the Godjeb and Gibbe of Eneara (Iniara); therefore in the high mountains of Habesch, in 7° 20′ N. latitude, and 33° E. long. from Paris, or 35° 22′ from Greenwich. He conjectures that the Arabs, from a similarity of sound, may have interpreted the native name Gamaro belonging to the Abyssinian mountains, in the south-west of Gaka in which the Godjeb (or White Nile?) has its source, to mean Moon Mountains (Djebel al-Kamar); so that Ptolemy himself, familiar with the intercourse between Abyssinia and the Indian Ocean, may have taken the Semitic version, given by early Arab immigrants. (Compare Ayrton in the Journal of the Royal Geogr. Soc. vol. xviii. 1848, p. 53, 55, and 59-63, with Fred. Werne’s instructive expedition for the discovery of the sources of the Nile, Exped. zur Entd. der Nil-Quellen, 1848, S. 534-536.)

The lively interest which has again been excited in England for the discovery of the most southern sources of the Nile, induced the above-named Abyssinian traveller, Charles Beke, at the recent meeting of the British Association for the Advancement of Science, held at Swansea, August 1848, to develop more in detail his ideas respecting the connection between the Mountains of the Moon and the Mountains of Habesch. He says:--“The Abyssinian elevated plain, generally above 8000 feet high, extends towards the south to nearly 9° or 10° N. latitude. The eastern declivity of the highlands has to the inhabitants of the coast the appearance of a mountain chain. The plateau at its southern extremity passes into the Mountains of the Moon, which run, not east and west, but parallel to the coast, or from NNE. to SSW.; extending from 10° N. to 5° S. latitude. The sources of the White Nile are situated in the Mono-Moezi country, probably in 2-1/2° S., not far from where the river Sabaki, on the eastern side of the Mountains of the Moon, falls into the Indian Ocean near Melindeh, north of Mombaza. Last autumn (1847) the two Abyssinian missionaries Rebmann and Krapf were still on the coast of Mombaza. They have established in the vicinity, among the Wakamba tribe, a missionary station called Rabbay Empie, which promises to be very useful also for geographical discovery. Families belonging to the Wakamba tribe have advanced to the west five or six hundred miles into the interior of the country, as far as the upper course of the river Lusidji, the great lake Nyassi or Zambeze (5° S. lat.?), and the sources of the Nile which are not far distant. An expedition to these sources, which Herr Friedrich Bialloblotzky, of Hanover, is preparing to undertake, (by the advice of Beke), is to set out from Mombaza. The Nile coming from the west referred to by the ancients is probably the Bahr-el-Ghazal, or Keilah, which falls into the Nile in 9° N. lat., above the mouth of the Godjeb or Sobat.”

Russegger’s scientific expedition,--which by Mehemet Ali’s desire was sent to the gold-washings of Fazokl on the Blue (Green) Nile, Bahr-el-Azrek, in 1837 and 1838,--had made the existence of the “Mountains of the Moon” appear very doubtful. The Blue Nile, the Astapus of Ptolemy, issuing from the lake of Coloe (now called lake Tzana) winds from amongst the colossal Abyssinian mountains; but towards the south-west an extensive low tract of country appears. The three exploring expeditions sent by the Egyptian government, (one in November 1839 from Chartum to the confluence of the Blue and the White Nile, under the command of Selim Bimbashi; another in the autumn of 1840, which was accompanied by the French engineers Arnaud, Sabatier, and Thibaud; and a third in August 1841), first unveiled the high mountains which, between the parallels of 6°-4°, and probably still farther to the south, run at first from west to east, and afterwards from north-west to south-east, and approach the left bank of the Bahr-el-Abiad. The second of Mehemet Ali’s expeditions first saw the mountain chain, according to Werne’s account, in lat. 11-1/3° where Gebel Abul and Gebel Kutak rise to 3400 (3623 Eng.) feet. The high land continued and approached nearer to the river more to the south, between 4-3/4° lat., to the parallel of the island of Tschenker in 4° 4′, where the expedition of Commander Selim and Feizulla Effendi terminated. The shallow river makes its way between rocks, and detached mountains rise again in the country of Bari to 3000 (3197 Eng.) feet. These probably belong to the Mountains of the Moon as represented in our most recent maps, although they are not indeed mountains covered with perpetual snow such as Ptolemy had described (lib. iv. cap. 9). The limit of perpetual snow in these latitudes would not certainly be found below an elevation of 14500 (15450 Eng.) feet. Perhaps Ptolemy transferred to the country of the sources of the White Nile the knowledge which he may have had of the high mountains of Habesch, which are nearer to Upper Egypt and to the Red Sea. In Godiam, Kaffa, Miecha, and Sami, the Abyssinian mountains rise to 10000 and 14000 (10657 and 14920 Eng.) feet, according to exact measurements; not according to Bruce, who gives the elevation of Chartum exceedingly wide of the truth, _i. e._, 4730 (5041 Eng.) feet, instead of 1430 (1524 Eng.) feet! Rüppell, one of the most accurate observers of the present day, found Abba Jaret, in 13° 10′ of latitude, only 66 (70 Eng.) feet lower than Mont Blanc. (Compare Rüppell, Reise in Abyssinien, Bd. i. S. 414, and Bd. ii. S. 443). Rüppell found, adjoining the Buahat, an elevated plain 13080 (13939 Eng.) feet above the Red Sea, barely covered with a small quantity of fresh fallen snow (Humboldt, Asie Centrale, T. iii. p. 272). The celebrated inscription of Adulis, which Niebuhr considers to be somewhat later than Juba and than Augustus, also speaks of Abyssinian snow “that reaches to the knees.” This is, I believe, the earliest mention in antiquity of snow within the tropics (Asie Centrale, T. iii. p. 235); as the Paropanisus is 12° of latitude north of the northern limit of the torrid zone.