Chapter XVII: Scientific Intelligence (8)

The feeder of the lake coming down from the north was described only by the natives; but its water being very clear, even during its annual risings, and these being incomprehensible to the inhabitants of that part of the country, this course may be expected to be long, and not improbably rising from a snowy mountain.

The effluent of the lake, the Zonga, was travelled along by Mr L. for 300 miles; as the water was clear, the stream placid, the banks thickly clothed with beds of reeds, and the height above the sea 2200 feet,--it may be presumed that this river does _not_ communicate with the ocean, and that it is gradually dissipated like other rivers there by evaporation and absorption.

The banyan, the palmyra, and the baobab, taking the place of the cactus, aloe, euphorbia and acacia, indicate the arrival in a better watered country and a totally different botanical region than any previously reached from the Cape.

The inhabitants of the lake "Bayeiye," seem to be a new race; their language was unknown; and they possess several remarkable habits and customs totally at variance with the characteristics of all the South African tribes, Hottentots, Bushmen, Caffres, Bechuana, Zoolahs, &c., south of the tropics; as for instance, their having _canoes_, killing the hippopotami with harpoons attached to ropes, and catching fish in nets.

The head of a fish which abounds in the lake, as well as a fearful fly which stings the oxen to death, have been sent home, and are declared to be new.

In conclusion, we have the pleasure of adding that although the Geographical Society could not exactly award with propriety their Royal gold medal to discoveries in their science; made in a secondary point of view, and but indifferently described, when it should be reserved for a Bruce or a Humboldt,--yet they have with great satisfaction and alacrity awarded the value of the medal in money; and it is devoutly to be hoped that Mr L. may be spared to continue the exploration which he has thus auspiciously begun. P. S.

_Letter from the Rev. David Livingston, addressed to the
Rev. Arthur Tidman, Foreign Secretary, London Missionary Society._

_Banks of the River Zonga, 3rd September 1849._

DEAR SIR,--I left my station, Kolobeng (situated 25° South lat.,
26 East long.), on the 1st of June last, in order to carry into
effect the intention, of which I had previously informed you, viz.
to open a new field in the North, by penetrating the great
obstacle to our progress, called the Desert, which, stretching
away on our West, North-West, and North, has hitherto presented an
insurmountable barrier to Europeans.

A large party of Griquas, in about thirty waggons, made many and
persevering efforts at two different points last year; but, though
inured to the climate, and stimulated by the prospect of much gain
from the ivory they expected to procure, want of water compelled
them to retreat.

Two gentlemen, to whom I had communicated my intention of
proceeding to the oft-reported lake beyond the desert, came from
England for the express purpose of being present at the discovery,
and to their liberal and zealous co-operation we are especially
indebted for the success with which that and other objects have
been accomplished. While waiting for their arrival, seven men came
to me from the Batavana, a tribe living on the banks of the lake,
with an earnest request from their chief for a visit. But the path
by which they had come to Kolobeng was impracticable for waggons;
so, declining their guidance I selected the more circuitous route,
by which the Bermangueato usually pass, and, having Bakwains for
guides, their self-interest in our success was secured by my
promising to carry any ivory they might procure for their chiefs
in my waggon; and right faithfully they performed their task.

When Sekhomi, the Bermangueato chief, became aware of our
intentions to pass into the regions beyond him, with true native
inhumanity he sent men before us to drive away all the bushmen and
Bakalihari from our route, in order that, being deprived of their
assistance in the search for water, we might, like the Griquas
above mentioned, be compelled to return. This measure deprived me
of the opportunity of holding the intercourse with these poor
outcasts I might otherwise have enjoyed. But through the good
providence of God, after travelling about 300 miles from Kolobeng,
we struck on a magnificent river on the 4th of July, and without
further difficulty, in so far as water was concerned, by winding
along its banks nearly 300 miles more, we reached the Batavana, on
the lake Ngami, by the beginning of August.

Previous to leaving this beautiful river on my return home, and
commencing our route across the desert, I feel anxious to furnish
you with the impressions produced on my mind by it and its
inhabitants, the Bakoba or Bayeiye. They are a totally distinct
race from the Bechuanas. They call themselves Bayeiye (or men),
while the term Bakoba (the name has somewhat of the meaning of
"slaves,") is applied to them by the Bechuanas. Their complexion
is darker than that of the Bechuanas; and, of 300 words I
collected of their language, only 21 bear any resemblance to
Sitchuana. They paddle along the rivers and lake in canoes
hollowed out of the trunks of single trees; take fish in nets made
of a weed which abounds on the banks; and kill hippopotami with
harpoons attached to ropes. We greatly admired the frank, manly
bearing of these inland sailors. Many of them spoke Sitchuana
fluently, and, while the waggon went along the bank, I greatly
enjoyed following the windings of the river in one of their
primitive craft, and visiting their little villages among the
reed. The banks are beautiful beyond any we had ever seen, except
perhaps some parts of the Clyde. They are covered, in general,
with gigantic trees, some of them bearing fruit, and quite new.
Two of the Baobab variety measured 70 to 76 feet in circumference.
The higher we ascended the river, the broader it became, until we
often saw more than 100 yards of clear deep water between the
broad belt of reed which grows in the shallower parts. The water
was clear as crystal, and as we approached the point of junction
with other large rivers _reported to exist_ in the North, it was
quite soft and cold. The fact that the Zonga is connected with
large rivers coming from the north awakens emotions in my mind,
which make the discovery of the lake dwindle out of sight. It
opens the prospect of a highway, capable of being quickly
traversed by boats, to a large section of well-peopled territory.

One remarkable feature in this river is its periodical rise and
fall. It has risen nearly three feet in height since our arrival,
and this is the dry season. That the rise is not caused by rains
is evident from the water being so pure. Its purity and softness
increased as we ascended towards its junction with the Tamunakle,
from which, although connected with the lake, it derives the
present increased supply. The sharpness of the air caused an
amazing keenness of appetite, at an elevation of little more than
2000 feet above the level of the sea (water boiled at 207½°
thermometer), and the reports of the Bayeiye, that the waters came
from a mountainous region, suggested the conclusion that the
increase of the water, at the beginning and middle of the dry
season, must be derived from melting snow.

All the rivers reported, to the north of this, have Bayeiye upon
them, and there are other tribes on their banks. To one of these,
after visiting the Batavana, and taking a peep at the broad part
of the lake, we directed our course; but the Batavana chief
managed to obstruct us, by keeping all the Bayeiye near the ford
on the opposite bank of the Zonga. African chiefs invariably
dislike to see strangers passing _them to tribes beyond_.
Sebitoane,--the chief who in former years saved the life of
Sechele our chief,--lives about ten days north-east of the
Batavana. The latter sent a present as a token of gratitude. This
would have been a good introduction; the knowledge of the
language, however, is the _best_ we can have. I endeavoured to
construct a raft, at a part which was only fifty or sixty yards
wide, but the wood, though sun-dried, was so heavy it sunk
immediately; another kind would not bear my weight, although a
considerable portion of my person was under water. I could easily
have swam across, and fain would have done it; but, landing
without clothes, and then demanding of the Bakoba the loan of a
boat, would scarcely be the thing for a messenger of peace, even
though no alligator met me in the passage. These and other
thoughts were revolving in my mind as I stood in the water,--for
most sorely do I dislike to be beaten,--when my kind and generous
friend Mr Oswell, with whom _alone_ the visit to Sebitoane was to
be made, offered to bring up a boat at his own expense from the
Cape, which, after visiting the chief, and coming round the north
end of the lake, will become missionary property. To him and our
other companion Mr Murray, I feel greatly indebted,--_for the
chief expense of the journey has been borne by them_. _They_ could
not have reached this point without my assistance; but, for the
aid they have rendered in opening up this field, I feel greatly
indebted; and, should any public notice be taken of this journey,
I shall feel obliged to the directors if they express my
thankfulness.

The Bayeiye or Bakoba listened to the statements made from the
Divine Word with great attention, and, if I am not mistaken,
seemed to understand the message of mercy delivered better than
any people to whom I have preached for the _first_ time. They have
invariably a great many charms in the villages; stated the name of
God in their language (without the least hesitation) to be
"Oreeja;" mentioned the name of the first man and woman, and some
traditionary statements respecting the flood. I shall not,
however, take these for certain, till I have more knowledge of
their language. They are found dwelling among the reed all round
the lake, and on the banks of all the rivers to the north.

With the periodical flow of the rivers great shoals of fish
descend. The people could give no reason for the rise of the
water, further than that a chief, who lives in a part of the
country in the north, called Mazzekiva, kills a man annually and
throws his body into the stream, after which the water begins to
flow.

The sketch which I enclose is intended to convey an idea of the
river Zonga and the lake Ngami. The name of the latter is
pronounced as if written with the Spanish ñ, the _g_ being
inserted to shew that the ringing sound is required. The meaning
is "Great Water." The latitude, taken by a Sextant on which I can
fully depend, was 20° 20´ south, at the north-east extremity,
where it is joined by the Zonga; longitude about 24° east. _We do
not, however, know it with certainty._ We left our waggon near the
Batavana town, and rode on horseback about six miles beyond it to
the broad part. It gradually widens out into a Firth about 15
miles across, as you go south from the town, and in the
south-south-west presents a large horizon of water. _It is
reported_ to be about 70 miles in length, bends round to the
north-west, and there receives another river similar to the Zonga.
The Zonga runs to the north-east. The thorns were so thickly
planted near the upper part of this river, that we left all our
waggons standing about 180 miles from the lake, except that of Mr
Oswell, in which we travelled the remaining distance; but for this
precaution our oxen would have been unable to return. I am now
standing at a tribe of Bakurutse, and shall in a day or two
re-enter the desert.

The breadth marked is intended to show the difference between the
size of the Zonga, after its junction with the Tamunakle and
before it. The farther it runs east, the narrower it becomes. The
course is shewn by the arrow-heads. _The rivers not seen, but
reported by the natives_, are put down in dotted lines. The dotted
lines running north of the river and lake, shew the probable
course of the Tamunakle, and another river which falls into the
lake at its north-west extremity. The arrow-heads shew also the
direction of _its_ flow. At the part marked by the name of the
Chief Mosing it is not more than 50 or 60 yards in breadth, while
at 20° 7´ it is more than 100, and very deep.

The principal disease reported to prevail at certain seasons
appears, from the account of the symptoms the natives give, to be
pneumonia and not fever. When the wind rises to an ordinary
breeze, such immense clouds of dust arise from the numerous
dried-out lakes called salt-pans, that the whole atmosphere
becomes quite yellow, and one cannot distinguish objects more than
two miles off. It causes irritation in the eyes, and, as wind
prevails almost constantly at certain seasons, this impalpable
powder may act as it does among the grinders in Sheffield. We
observed cough among them, a complaint almost unknown at Kolobeng.
Musquitoes swarm in summer, and the Banyan and Palmyra give in
some parts an Indian cast to the scenery.

(Signed) DAVID LIVINGSTON.

_A Brief Sketch of the Geology of the West Indies,
from_ Dr DAVY'S _Lectures on the Study of Chemistry,
drawn up chiefly from the Author's own Observations_.[88]
Communicated for the Philosophical Journal.

Footnote 88: Lectures on the Study of Chemistry, in connection
with the Atmosphere, the Earth and the Ocean, and Discourses on
Agriculture, with Introductions on the present State of the West
Indies, and on the Agricultural Societies of Barbados. By JOHN
DAVY, M.D., F.R.S., &c. London, Longmans. 1850.

In the preceding lecture, I brought under your notice the antagonist and compensating, or correcting influences of animal life in preserving the uniformity of composition of the atmosphere. In the earth we witness influences of the like kind, as it were opposed to each other, and producing opposite effects. Water, in its operation, aided by air, may be considered as destructive, wearing away rocks and mountains, and carrying their comminuted parts to lower levels, and even into the sea, to be buried in its depths. Fire may be considered as restorative; acting below the surface, it melts and also consolidates, according to its degree of intensity, tending to reproduce crystalline rocks in one instance, and stratified in the other. Even when it appears most eminently to act according to our ordinary notions of its operation as a devastating and destroying agent, for example, in the eruption of a volcano, the ashes which are discharged into the atmosphere, and are widely scattered by the winds, even when they fall on the adjoining countries, may help to supply the place of the old surface-materials, carried away by streams and floods, and to renovate the soil with new elements of fertility. And acting in another form and manner, the same power which occasions volcanic eruptions appears to be productive of another effect, viz., the gradual elevation of the bed of the sea, tending to the formation of new land, of which we seem to have examples in the extension of certain coasts, and the appearance of rocks and dry land above the waves, preceded by a gradual diminution of the water over the spots where these remarkable phenomena occur.

Of most of the geological changes alluded to in the preceding remarks, the West Indies afford well marked instances.

From the continent of America are to be seen vast rivers flowing into the sea, turbid with the detritus of the country through which they have descended in a course of thousands of miles, and discolouring and freshening the waters with which they mix at an extraordinary distance from land. Between their mouths on the coasts and their rapids in the boundary hills of the interior, immense level, or almost level tracts occur,--marsh, morass, and sandbank, neither land nor water, covered chiefly with aquatic plants,--tracts formed by deposits from the great rivers, and commonly of materials somewhat coarser and heavier than those which are longer suspended and are carried out into the sea in consequence of their greater fineness.

In many of the islands not only are there rocks to be seen evidently of volcanic origin--columnar basalt, trachyte, and many varieties of tufa, but also craters from whence eruptions have taken place, and in which the fires are hardly yet extinct that once acted, as is indicated by the hot steams and exhalations still proceeding from them.

Moreover, in some of these islands, rocks of volcanic origin, crystalline in their structure, and totally destitute of organic remains, are associated with others of a perfectly different character, stratified and abounding in organic remains,--various species of sea shells and of coral; and it is worthy of notice, that, in one of the instances in which the appearance is best observed, viz., at Brimstone Hill, in St Christopher's, the volcanic rock, flanked by the stratified rock, and the latter--an aggregate of shells, coral, and calcareous marl, has its strata highly inclined, tilted up as it were by the former.

Other islands, or parts of islands, occur, in which there are only partial volcanic traces, and these not so much of volcanic action and disturbance on the spot, as of materials, such as ashes, thrown up by volcanoes, and those distant ones. The island Barbados is an example. Composed in great parts of a calcareous aggregate, in which organic remains abound, it has very much the character, in its peculiar features, of having been raised from the bed of the ocean (where it is certain it was formed), by some mighty force, slowly acting, and which, it is probable, is acting still.

Nor is there wanting in these seas instances of islands, in which almost every variety of formation is exemplified. Barbados, in its smaller portion--the Scotland district, exhibits some interesting varieties, such as beds of chalk abounding in the remains of microscopic animalcules, strata of sandstone, some siliceous, some calcareous; the one without organic remains, containing, however, deposits of coal and bitumen; the other--the latter having included in them organic remains, and of a kind to connect them with the calcareous rock of which the larger portion of the island is formed, for instance, the spines of echini and the teeth of squali. The larger islands, Trinidad and Jamaica, Port Rico, and Cuba, yield examples, still more in point. In Trinidad I am not aware that any volcano, or crater of one, has been discovered, or any rocks evidently volcanic in their origin; but from the imperfectly crystalline rocks, destitute of organic remains and distinct stratification, to clays and marls, to mud eruptions or volcanoes as these are sometimes called, through limestones and sandstones stratified, and containing organic remains, a tolerably well-marked series may be traced. In the adjoining and smaller island Tobago some of the same series are observable, but in a broken manner, not a little interesting and instructive. There, highly crystalline rocks, destitute of organic remains, are in juxtaposition with others abounding in these remains; coral rock is even found resting on granite; and in another situation the latter rock is contiguous to mica slate, in which quartz in mass is not of rare occurrence.

_On the Differences between Progressive, Embryonic, and Prophetic
Types in the Succession of Organized Beings through
the whole Range of Geological Times._

It was a great improvement in our zoological investigations when the differences in their relations, according to the various degrees of affinity or analogy which exist between animals, were pointed out, and successively better understood. In earlier times, zoologists made no distinction between the different relations which existed among animals. Affinity and analogy, so dissimilar in their essential characters, were constantly mistaken one for the other; and upon the peculiarities which struck the observer most at first sight, animals were brought together, sometimes upon the ground of true affinity, sometimes, also, upon the ground of close analogy; and though comparative anatomy did put the mistakes arising from such confusion right, by showing that external appearances were sometimes deceptive, and that a more intimate knowledge of internal structure was necessary fully to understand the real relations between animals, there remained, nevertheless, a degree of uncertainty in many cases, as long as the principles of affinities and of analogies were not fully distinguished. Every naturalist now knows that true relationship--affinity--depends upon a unity in structure, however diversified the forms may be under which their fundamental structure is displayed. For instance, the affinity of whales and the other mammalia was not understood before it was shown that, under the form of fishes, these animals had truly the same structure as the highest _vertebrata_.

Again, the forms of _cetacea_ exemplify the analogy there is between whales and fishes. They are _related_ to mammalia; they are _analogous_ to fishes; they bear close affinity to the mammals which nurse their young with milk; they have rather close analogy to the gill-breathing fishes.

Since the fossil animals which have existed during former periods upon the surface of our globe, and which have successively peopled the ocean and the dry land, have been more carefully studied than they were at the beginning of these investigations; since they are no longer considered as mere curiosities, but as the earlier representatives of an order of things which has been gradually and successively developed throughout the history of our globe, facts have been brought to light which now require a very careful examination, and will lead to a more complete understanding of the various relations which exist between these extinct types and those which still continue to live in our days. Upon close comparison of these facts, I have been led to distinguish two sorts of relations between the extinct animals, and those of our days, which seem to me to have been either overlooked or not sufficiently distinguished. Indeed, the general results derived from Palæontological investigations, seem scarcely to have gone beyond showing that the animals of former ages are specifically and frequently also generically distinct from those of the present creation; and also to establish certain graduation between them, agreeing more or less with the degree of perfection which we recognise between the living animals according to their structure.

It is now pretty generally understood that fishes, which rank lowest among the _Vertebrata_, have existed alone during the oldest periods; that the reptiles which, in the gradation of structure, rank next above them, have followed at a later period; that still later the birds, which, according to their anatomy, rank above reptiles, have next made their appearance; and that mammalia, which stand highest, have been introduced last, and even among these the lower families seem to have been more numerous, before the higher ones prevailed over them. Man, at last, has been created, only after all other types had acquired their full development. These facts which, in such generality are fully exemplified in every country in the order of succession of the different fossil characteristics of the various geological deposits, shew plainly that a gradation really exists in this succession, and constitutes one of the most prominent characters of the development of the animal kingdom as a whole.

If we investigate, however, this gradation, and the order of succession of animals more closely, we cannot but be struck with the different relations which exist between the fossils and the living animals. Many extinct types have been pointed out as characteristic of different geological periods, which combine, as it were, peculiarities which at present are found separately in different families of animals.

I may mention as such, the _Ichthyosaur_, with their fish-like vertebræ, their dolphin or porpoise-like general form, and several special characters reminding us of their close relation to the Crocodilian reptiles; thus combining characters of different classes in the most extraordinary manner.

Again, the _Pterodactyli_, in which reptilian characters are combined with peculiarities reminding us both of birds and bats.

Again, the large carnivorous fishes of the coal period, combining peculiarities of the _Saurians_, with true fish characters; and so on.

These relations are of an entirely different kind from those which I have pointed out between some of the older fossils and the early stage of growth of the living representatives of the same families.

For instance, the fossil fishes with a heterocercal tail, found below the new red sandstone, down to the lowest deposits, reminds us of the peculiar termination of the vertebral column in all fish embryos of species living in the present period, to whatever family they may belong, indicating a similarity of structure in the oldest representative of this class, with the earliest condition of the germs of those animals in our days.

Let us now examine whether we can properly understand the bearings of these relations, and the meaning of such differences.

In the first place, I have mentioned the gradual progress, which is observed in the succession of the different classes of _Vertebrata_. This progress is exemplified by a series of types which differ from each other, but which shew, when arranged in a series, a gradation which agrees in general with the structural gradation, which we may establish upon anatomical evidence. For instance, the salamanders, with their various forms, rank below the tailless _Batrachians_.

And where we have a succession of those animals in the tertiary deposits as they occur in various parts of Europe, we may fairly say that the fossils form, in their succession, a series of progressive types.

Another example may perhaps illustrate the point more fully. The _orthocera_ of the oldest periods precede the curved lituites, which, in their turn, are followed by the circumvolute nautilus. Here, again, we have a natural gradation of a series of progressive types. Again, among _crinoids_, we find, in the older deposits, a variety of species resting upon a stem, while free crinoids begin to appear only during the secondary deposit and prevail, in the present creation, over those attached to the soil. Here, again, we have a series of progressive types developed successively, which are apparently independent of each other and seem to bear no other relation to each than that arising from the general character of the group to which they belong. Such types exemplify simply in the groups to which they belong, a real progress in the successive development of the peculiarities which characterise them as natural divisions among animals. Such forms I shall call _Progressive Types_.

The relations, however, which are exemplified in the oldest fishes, in the ichthyosaurians, in the pterodactyls or in the megalosaurians, seem to me to be clearly of a different character, and to differ from simple progressive types, inasmuch as those which appear earlier, combine peculiarities which, at a later period, appear separately in distinct forms. For instance, the reptilian characters which we recognise in the sauroid fishes, are developed at a later period in animals no longer belonging to the class of fishes, but constituting by themselves new types, provided with additional peculiarities which separate them fully from the fishes in general, as well as from those fishes in which we recognise some relation to reptiles during a period when no reptile existed.

Again, the ichthyosaurians, though true reptiles appearing long after fishes had been called into existence, and during an early period of the history of the reptiles, still shew their relation to fishes by the character of their vertebral column, and foreshadow, as it were, in their form, the cetacea of later ages, as well as many forms of the gigantic saurians of the secondary period. The same may be said of the pterodactyls, which are also true reptiles, but, in which the anterior extremity foreshadow peculiarities characteristic of birds and bats. Such types I shall call _Prophetic Types_.

To an analytic mind the examination of the peculiarities of such animals may foretell a higher progress of development, carried out in real existence, only during a later period, even if he had never seen the later ones; for in such types the germs of a future development may be recognised, and upon close examination, truly referred to the peculiarities of other higher groups, even if the intermediate links remained unknown, which, however, as the matter now stands, can leave no doubt in our mind that these prophetic types really foreshadowed that diversity of forms which has been created since they have gone by. We may also say that these prophetic types lay before us the course of thoughts which has been carried out in the plan of creation by the Supreme intelligence, who called them into existence in rich order of succession, and in so diversified relations. The recognition of this prophetic character of certain types of extinct animals is not only important in a philosophical point of view; I have no doubt it will ultimately and rapidly lead to a better, fuller, higher, and deeper understanding of the various relations which exist between animals. Let me at once point to some of these relations which might never have been understood but for this appreciation.

Among Crinoids, we have not only progressive types, as I have already quoted, but we have also prophetic ones. The Cystidæ are truly prophetic of the Echini proper. I may only mention the genus Echinocrinus to shew the link.

The Pentremites, again, are the prophetic type foreshadowing the star-fishes. And often in subordinate groups we may find such close relations between genera of the same minor divisions; such, for instance, as the genus Encrinus, in which the genera Apiocrinus and Pentacrinus, are simultaneously foreshadowed. Perhaps, in this case, a distinction might be introduced between truly prophetic types and synthetic types, in which the characters of later groups are rather more combined than really foreshadowed.

As for the relation between older types and the embryos of the living representatives of the same families which are so extensively observed in almost all groups of the animal kingdom, which have existed during earlier periods, it may best be expressed if we call those fossils which exemplify, in full grown animals, forms which exist at present only in the earliest stages of growth of our living animals, _Embryonic Types_, in counterdistinction from the progressive types, and from the prophetic types. These embryonic types may be purely such, or they may be at the same time either progressive types, or even prophetic types. I shall call purely embryonic types those in which we recognise peculiarities characteristic of the embryo of the same family. For instance, the older Sauroids, which have the upper lobe of the tail prolonged, or the common Crinoids provided with a stem, which resemble the young Comatulæ, &c., &c. I shall distinguish, as progressive embryonic types, those in which we recognise simultaneously a relation to the embryo of the same family, when they form besides a link in the natural chain of progressive development. Such, for instance, as the oldest Salamanders, or the earliest Sirenoid Pachyderm. Finally, I shall call prophetic embryonic types those in which we have embryonic characters, combined with the peculiarities which stamp the type as a prophetic one, such, for instance, as the Echinoid and Asteroid Crinoids of the former ages.

The fact that these different types may thus present complications of their character, or appear more or less pure and typical, goes further to shew how deeply diversified the plan of creation is, and how many relations should be simultaneously understood before we are prepared to have a full insight into the plan of creation. There we see one type forming simply, and alone, the first link of a progressive series. There we see another which foreshadows types, which appear isolate afterwards. There we see a third, which, in its full development, exemplifies a state which is transient only in higher representatives of the same family. And then, again, we see these different relations running into each other, and reminding us that, however difficult it may be for us to see at one glance all this diversity of relations, there is, notwithstanding, an intelligence which not only conceived these various combinations, but called them into real existence in a long succession of ages.--_L. Agassiz in the American Association for the Advancement of Science_, August 1849.

_On a new Analogy in the Periods of Rotation of the Primary
Planets discovered by Daniel Kirkwood of Pottsville, Pennsylvania._

At the recent meeting of the Association for the Advancement of Science, an announcement was made, which, if it is found to be correct, will be regarded as relating to one of the most important discoveries which have been made in astronomy for years. It is no less than a new law of the solar system, closely resembling those of Kepler, which form the groundwork of many of the problems of astronomy. Mr S. C. Walker read to the Association a letter from Mr Daniel Kirkwood, of Pottsville, Pa., the discoverer of this new law, from which we make some extracts, omitting all that refers to the higher branches of mathematics.

"While we have in the law of Kepler a bond of mutual relationship between the planets, as regards their revolutions around the sun, it is remarkable that no law regulating their rotations on their axes has ever been discovered. For several years I have had little doubt of the existence of such a law in nature, and have been engaged, as circumstances would permit, in attempting its development. I have at length arrived at results, which, if they do not justify me in announcing the solution of this important and interesting problem, must at least be regarded as astonishing coincidences."

After stating some equations, he gives the following tables as the data on which he has proceeded:--

+---------+---------------+-------------+-----------+----------------+
| | Mean dist. | | Square |No. of rotations|
|Planet's | from the sun | Mars. | root of | in one sid. |
| name. | in miles. | | Mars. | period. |
+---------+---------------+-------------+-----------+----------------+
|Mercury, | 36,814,000 | 277,000 | 526·3 | 87·63 |
|Venus, | 68,787,000 | 2,463,836 | 1·569·6 | 230·90 |
|Earth, | 95,103,000 | 2,817,409 | 1·678·5 | 366·25 |
|Mars, | 144,908,000 | 392,735 | 626·7 | 669·60 |
|Jupiter, | 494,797,000 | 953,570,222 | 30·879·8 | 10·471·00 |
|Saturn, | 907,162,000 | 284,738,000 | 16·874·1 | 24·620·00 |
|Uranus, | 1,824,290,000 | 35,186,000 | 5·931·5 | |
+---------+---------------+-------------+-----------+----------------+

From these data he deduces the following law:--"The square of the number of a primary planet's days in its year, is as the cube of the diameter of its sphere of attraction in the nebular hypothesis."

"The points of equal attraction between the planets severally (when in conjunction), are situated as follows:--

Miles from the Miles from the
former. latter.

Between Mercury and Venus, 8,029,600 23,943,400
" Venus and the Earth, 12,716,600 13,599,400
" Earth and Mars, 36,264,600 13,540,400
" Jupiter and Saturn, 266,655,000 145,710,000
" Saturn and Uranus, 678,590,000 238,538,000

"It will be seen from the above, that the diameter of the earth's sphere of attraction is 49,864,000 miles. Hence the diameters of the respective spheres of attraction of the other planets, according to my empirical law, will be found to be as follows:--

Diameter of sphere
of Attraction.
Mercury, 19,238,000
Venus, 36,660,000
Mars, 74,560,000
Jupiter, 466,200,000
Saturn, 824,300,000

"The volumes of the sphere of attraction of Venus, Mars, and Saturn in this table, correspond with those obtained from the preceding one; that of Mars extending 61,000,000 miles beyond his orbit, or to the distance of 206,000,000 miles from the sun. This is about 2,000,000 or 3,000,000 miles less than the mean distance of Flora, the nearest discovered asteroid. That of Mercury extends about 11,000,000 miles within the orbit; consequently, if there be an undiscovered planet interior to Mercury, its distance from the Sun, according to my hypothesis, must be less than 26,000,000 miles. Jupiter's sphere of attraction extends only about 200,000,000 of miles within his orbit, and leaving 89,000,000 miles for the asteroids. It is only in the most distant portion of this space, where small bodies would be likely to be detected, that none have yet been discovered."

Mr Kirkwood then modestly concludes:--

"The foregoing is submitted to your inspection with much diffidence. An author, you know, can hardly be expected to form a proper estimate of his own performance. When it is considered, however, that my formula involves the distances, masses, annual revolutions, and axial rotations of all the primary planets in the system, I must confess I find it difficult to resist the conclusion, that the law is founded in nature."

After this letter had been read, Mr Walker said, that, induced by the importance of the subject, he had at once proceeded to verify the data and conclusions of Mr Kirkwood, and had found that there was nothing in them requiring modification, except, perhaps, the substitution of some more recent values for the masses of Mercury and Uranus. This theory and that of Laplace, with reference to nebulæ, mutually strengthen each other; although the latter has been a mere supposition, while the former rests upon a mathematical basis. In a later letter, which was also read, Mr Kirkwood says that he has pursued this subject for the last ten years, it having been first suggested to him by the nebular hypothesis, which he thought could be established by some law of rotation.

Mr Walker then entered into a lengthened examination of the data on which the law rests, and seemed to come to the conclusion, that, as far as we know at present, everything is in favour of the truth of the law, except that it requires the assumption of another planet between Jupiter and Mars.

Mr Walker closed his examination by saying, "We may, therefore, conclude, that, _whether Kirkwood's analogy is or is not the expression of a physical law, it is, at least, that of a physical fact in the mechanism of the universe_. The quantity on which the analogy is based has such immediate dependence upon the nebular hypothesis, that it lends strength to the latter, and gives new plausibility to the presumption that this, also, is a fact in the past history of the solar system.

"Such, then, is the present state of the question. Thirty-six elements of nine planets (four being hypothetical) appear to harmonize with Kirkwood's analogy in all the four fundamental equations of condition for each planet.

"To suppose that so many independent variable quantities should harmonize together by accident, is a more strained construction of the premises than the frank admission that they follow a law of nature.

"If, in the course of time, the hypotheses of Laplace and Kirkwood should be found to be the laws of nature, they will throw new light on the internal organization of the planets in their present, and in any more primitive, state through which they may have passed.

"For instance, we may compute the distance from the centre at which any planet must have received its projectile force, in order to produce, at the same time, its double movement of translation and rotation.

"If the planet, in a more primitive state, existed in the form of a ring revolving round the Sun, having its present orbit for that of the centre of gravity of the ring, the momentum of rotation must, by virtue of the principle of conservation of movement, have existed in some form in the ring. It is easy to perceive that this momentum is precisely the amount which must be distributed among the particles of the ring, in order to preserve to all the condition of dynamical equilibrium, while those of each generating surface of the ring were wheeling round with the same angular velocity.

"If the planets have really passed from the shape of a revolving ring to their present state, the prevalence of Kirkwood's analogy shews a nice adaptation of parts in every stage of the transition.

"If the primitive quantity of coloric (free and latent) had undergone a very great change beyond that now indicated in the cooling of their crusts; if the primitive quantity of movement of rotation had been different from its actual value for any planet; if the law of elasticity of particles for a given temperature and distance from each other varied from one planet to another in the primitive or present state; in either of these cases, the analogy of Kirkwood might have failed. As it is, no such failure is noticed; we are authorised, therefore, to conclude, that the primitive quantity of coloric, the law of elasticity, the quantity of movement of rotation, the past and present radii of percussion, the primitive diameter of the generating surface of the rings, and the present dimensions and density of the planets, have been regulated by a general law, which has fulfilled for all of them the four fundamental conditions of Kirkwood's hypothesis.

"We may extend the nebular hypothesis and Kirkwood's analogy to the secondary system. If they are laws of nature, they must apply to both. In the secondary systems, the day and month are the same. This fact has remained hitherto unexplained. Lagrange shewed that if these values were once nearly equal, a libration sets in round a state of perfect equality; but he offered no conjecture as to the cause of the primitive equality. On the nebular and Kirkwood's hypothesis, it would only be necessary that, upon the breaking up of the ring, the primitive diameter of the generating figure and law of relative density of layers should be preserved."

Professor Peirce, whose opinions will probably be regarded as of more value on such a subject than that of any other man in this country,--especially since his successful discussion with Leverrier,--remarked, that Kirkwood's analogy was the only discovery of the kind since Kepler's time that approached near to the character of his three physical laws. Bode's law, so called, was at best only an imperfect analogy. Kirkwood's analogy was more comprehensive, and more in harmony with the known elements of the system. The diameter of the sphere of attraction, a fundamental element in this analogy, now for the first time gave an appearance of reality to Laplace's nebular hypothesis which it never had before. The positive testimony in its favour would now outweigh the former negative evidence in the case, however strong it may have been. It follows at least from Kirkwood's analogy, that the planets were dependent upon each other, and therefore connected in their origin, whatever may have been the form of the connection, whether that of the nebular hypothesis, or some other not yet imagined.

At a later period of the meeting, M. B. A. Gould junior, stated that he had gone through the necessary calculations, using different quantities, and had come to the same conclusions as Mr Walker. He expressed his opinion, that at some future day the world will "speak of Kepler and Kirkwood as the discoverers of great planetary laws."

The members generally expressed the opinion, that Laplace's nebular hypothesis, from its furnishing one of the elements of Kirkwood's law, may now be regarded as an established fact in the past history of the solar system.--_American Annual of Scientific Discovery_, p. 335.

NOTE.--Such, at least, is rather a representation of American opinions than of our own. We are inclined to compare it more with Bode's law than with Kepler's. The former is a mere arithmetical accident, applying indifferently well to a portion only of the planets, and having nothing of reason to advance for its establishment. The latter are essential parts of mechanics and gravitation, and precisely and perfectly, and necessarily true, not only in every part of the solar system, but through the whole universe.

The fact of axial rotations being the groundwork of Kirkwood's analogy seems fatal to it, for gravitation takes no more account of the time of rotation of a planet than it does of specific gravity; all calculations of the movement of the body in space are equally independent of the one and the other.

Under these circumstances, the degree of accuracy with which it may be found to apply is the only saving clause. Messrs Walker and Gould investigating the subject independently, and with better constants of mass and distance than Kirkwood had been able to procure, declare that it appears _perfectly_! We are sorry that the late hour at which we have received this paper has prevented us either from giving it in full, or from testing the theory rigidly.

It will be observed that, according to Kirkwood's theory, in order to compute the time of axial rotations of any planet, it is necessary to have its mass and mean distance, together with the same quantities for the planets on either side of it. Now, these quantities are only obtainable for Venus, the Earth, Saturn, and Uranus (a planet being lost between Mars and Jupiter); and the rotation of Uranus not having been obtained as yet, there remains only the three first by which the theory can be tested.

In a preliminary calculation which we have instituted, we do not find the results so accordant as we had been led to expect, but still sufficiently so to give a certain probability of the approach to truth, in a case where the quantity had not been observed.

Viewed in this light, some very interesting results are obtained.

_1st_, The idea entertained by Bianchini and other observers, that the rotation of Venus is nearly 24 times as long as hitherto supposed, is utterly untenable.

_2d_, The time of rotation of Uranus, a quantity never yet observed (but doubtless capable of being observed by a telescope of Lord Rosse's calibre, _removed to a table-land in a tropical country_) is given; and appears so very different from any other yet observed, especially so from those of its neighbours Saturn and Jupiter, being = 1·396779, earth's = 0·997270 (sidereal rotation in mean solar days.)

_3d_, Knowing the rotations of Jupiter and Mars, we may supply, by using the analogy conversely, the _diameters of their spheres of attraction_, and thus get at the elements of the lost planet between Mars and Jupiter, and these appear to be:--mean distance = 2·9085111 (earth unity), mass in terms of Sun 1/1353240, sidereal rotation in earth's mean solar days 2·406104, and diameter of sphere of attraction 0·830951, in terms of earth's distance. The size is thus a little larger than Mars. The slowness of rotation is remarkable, especially in the case of a planet which is supposed since to have burst into pieces: the Americans have called it Kirkwood. P. S.

SCIENTIFIC INTELLIGENCE.

METEOROLOGY.

1. _Use of Coloured Glasses to assist the View in Fogs._--M. Lavini of Turin, in a letter to the editor of _L'Institut_ at Paris, makes the following curious observation, which, if confirmed, may prove to be of great importance:--"When there is a fog between two corresponding stations, so that the one station can with difficulty be seen from the other, if the observer passes a coloured glass between his eye and the eye-piece of his telescope, the effect of the fog is very sensibly diminished, so that frequently the signals from the other station can be very plainly perceived; when, without the coloured glass, even the station itself is invisible. The different colours do not all produce this effect in the same degree, the red seeming to be the best. Those who have good sight prefer the dark-red, while those who are short-sighted like the light-red better. The explanation of this effect seems to depend upon the fact, that the white colour of the fog strikes too powerfully upon the organ of sight, especially if the glass have a somewhat large field. But by the insertion of the coloured glass, the intensity of the light is much diminished by the interception of a part of the rays, and the observer's eye is less wearied, and, consequently, distinguishes better the outlines of the object observed."

2. _Ozone._--Chemists are not yet fully agreed concerning the nature or production of this singular substance, ozone. To Schonbein and Williamson we are indebted for most of our knowledge concerning it. The latter has supposed it to be a compound of oxygen and hydrogen, from the fact, that, when the ozone completely freed from moisture was passed over ignited copper, water was produced. De la Rive produced it by passing a current of electricity through pure dry oxygen gas contained in a receiver. It is also obtained in large quantities by passing oxygen gas over moistened phosphorous, and afterwards drying it. Thus prepared, it is a powerful chemical agent, possesses bleaching properties, oxidises the metals with rapidity, and destroys India-rubber. The hydrogen acids of sulphur are decomposed by it, water being formed by uniting with the hydrogen of the acid, and sulphur being set free. Professor Horsford has observed that ozone, subjected to a heat of 130° Fah., entirely loses its properties. Ozone, like chlorine, precipitates iodine, colouring a solution of iodide of potassium, and starch a deep blue colour. The peculiar smell, prevalent in the vicinity of objects struck by lightning, as well as that occasioned by the excitation of an electrical machine, and by the striking of two pieces of silica together, it is believed to be occasioned by ozone.--_Editors._--_Annual of Scientific Discovery_, p. 219.

_Method of Determining the Amount of Ozone in the Atmosphere._--At the meeting of the American Association, an instrument for determining the relative quantity of ozone in the air was presented by Professor Horsford. It consisted of a tube, containing at one end a plug of asbestus, moistened with a solution of iodide of potassium and starch. This plug within the tube, attached to an aspirator, would, as air passed over it, become blue. If much water flowed from the aspirator, and of course much air flowed over the asbestus before it became blue, the quantity of ozone indicated would be small. If but little water flowed (and this could be measured), the quantity of ozone indicated would be greater. The quantities of ozone would be inversely as the volumes of air passing through the tube before blueness is produced.--_Annual of Scientific Discovery_, p. 219.

HYDROGRAPHY.