I. Do those bones appear to have lain upon the furface of the earth from the first? Or,

II. Do they feem to have been originally at fome depth in the earth, and to have been afterwards exposed by the earth's falling away, or by its being washed away by floods, &c. ?

III. How far is that part of the marth from the river? How high above the common furface of the water of the river? And does it appear probable, from the level and face of that marfh, that in former times the river may have run where the bones are?

IV. How many elephants skeletons have been found, as far as may be collected from the number of tusks, or other marks? and at what distance from one another?

V. To send over, if poffible, a whole head, or the most entire parts of a head, especially of the upper jaw; and a foot, or the fmall bones of it, if they can be diftinguished; and any bones which have thofe parts pretty entire which once made a joint.

VI. To make correct drawings

of any of the bones which are pretty entire, if, on account of their fize, or tenderness, they cannot be fent over to England.

VII. If the bones do not lie in blended heaps, but thofe of one fingle animal all together, and at fome little distance from others, it might be of service towards afcertaining the species of this animal, to expofe or uncover one complete fett of bones, without moving any one of them from its place; and to make a general drawing of the whole, as they appear in that fituation; and to fend as many of them as are tolerably perfect over to England, with that drawing.

Lord Shelburne was pleased to take the care of this propofal upon himself; and in proper time will probably receive fuch information as may be fatisfactory.

I thought it would be adviseable, in the mean time, to collect all the information I could upon this fubject; and to lay the refult of fuch enquiries before this Society: that those who may have better opportunities might be invited to the fubject, and no longer leave fo capital an article of Natural History uncertain.

I examined all the foffil teeth, as they are called, in the Mufæum of this Society, and the head and teeth of an hippopotamus. Then, with Dr. Knight first, and a fecond time with Dr. Solander, I examined all the foffil teeth, and all the jaw-bones, and teeth of elephants, and hippopotami, and other large animals, in the British Mufæum; and fome likewise in private collections. In making this search, I met with grinders of the incognitum that were found in the

Brazils

Brazils and Lima, as well as in different parts of Europe.

At this time Lord Shelburne prefented the largest of the American tusks, and the jaw-bone, and fome grinders, to the British Mufæum ; and his lordship did me the honour to fend me the smaller tusk, and two grinders.

I went to four of the principal workers and dealers in ivory, with whom I faw and examined many hundreds of elephants teeth. Tho' they all affured me, that the real elephants teeth have often a fpiral twift, like a cow's horn, they could not fhew me one tooth fo twisted in all their collections, when I vifited them. Three of them did me the favour to come to my houfe; and they gave it as their opinion, that my two American tufks were genuine elephants teeth. One of them was even pofitive that they were African teeth. Another worker in ivory cut through that tusk which Lord Shelburne gave me. It proved to be found on the infide. He affured me that it was true elephantine ivory; and that workers in ivory could readily diftinguish the genuine, by its grain and texture, from all other bony fubftances whatever. He polished it: we compared it with other pieces of genuine ivory, and indeed they appeared to be perfectly fimilar. His opinion was afterwards confirmed by another experienced worker in ivory. Yet their opinion, and what I faw with my own eyes, convinced me of this fact only, viz. that true or genuine ivory is the production of two different animals; and not of the elephant alone.

Having thus collected all the materials to which I could have accefs,

To me

I carefully read what the French Academicians, Meffrs. Buffon and Daubenton, have written on this queftion, in the Hiftoire Naturelle, tom. XI. p. 86, &c. and p. 147, &c. tom. XII. p. 63; and Memoires de l'Acad. Roy. des Sc. Ann. 1762, p. 206. &c. But, inftead of meeting with facts which could difprove my opinion, I found obfervations and arguments which confirm it. One very material fact, which Mr. Daubenton furnifhes in fupport of my hypothefis, is the comparison of the American thigh-bone with that of a real elephant; both of which he has reprefented in figures, which appear to be done with accuracy. it seems most evident, that they are bones of two diftinct fpecies. The vaft difproportional thickness of the American bone, compared with that of the elephant, is furely more than we can attribute to the different proportions of bones, in the fame fpecies, which arise from age, fex, or climate. But Mr. Daubenton, to fupport his hypothesis, that the American femur is elephantine, is obliged to refer the great disproportion in thicknefs to the causes above-mentioned; and he affirms that in all other circumftances they are exactly alike. Now, to my eye, there is nothing more evident, than that the two femora differ widely in the fhape and proportion of the head; in the length and direction of the neck; and in the figure and direction of the great trochanter : fo that they have many characters, which prove their belonging to animals of different fpecies.

It may now be fairly prefumed that the American bones are proved to be certainly not elephantine: and whoever is of that opinion,

will naturally fufpect that the Siberian bones are of the fame kind. I imagine that it will be found, upon ftrict enquiry, to be fo. But, as I have not the neceffary materials for difcuffing this question at prefent, I fhall only ftate a few facts, to fhew that there is fome ground for the opinion.

1. All accounts, and particularly thofe of Meff. Gmelin, Buffon, and Daubenton, fay that the bones found in Siberia are larger than the bones of common elephants. This would make us inclined to fufpect that they were not elephants bones, but that they were of the incognitum.

2. The Siberian femur, as reprefented by Monfieur Daubenton, is very much like the American femur in fize, fhape, and proportions. This circumftance appears to be almost a demonftration, as we have before proved, that the American femur is not that of an elephant. And in this argument, we have even the weight of Monfieur Daubenton's opinion in our favour. For he (page 211) taking it for granted that the Siberian femur was undoubtedly elephantine, reafons from the likeness in fize, fhape, and proportions, that the American femur is fo. Now, as we have fhewn that the American femur is not elephantine, his proof taken from the fize, fhape, and proportions of the two bones, muft ferve to convince us that the Siberian thigh bone is not of the elephant, but of the incog

nitum.

1

3. Monfieur Daubenton found a

difference between the temporal bone brought from Siberia, and that of an elephant. This likewife is an argument in favour of our fuppofition.

4. The fuppofed elephant's tusk,

which was brought from Siberia by Mr. Bell, and prefented to Sir Hans Sloane, and of which we have a defcription and figure in the Memoirs of the Academy of Sciences at Paris (An. 1727. page 309), is evidently twisted like the tufk of the incognitum, and not at all like any elephant's tusk which I have ever feen. This proof will have confiderable weight with those who will take the trouble to examine that tusk in the British Mufæum.

In the last place it may be obferved, that as the incognitum of America has been proved to have been an animal different from the elephant, and probably the fame as the mammouth of Siberia; and as grinder teeth, like those of America, have been dug up in various other parts of the world; it should feem to follow, that the incognitum in former times has been a very general inhabitant of the globe. And if this animal was indeed carnivorous, which I believe cannot be doubted, though we may as philofophers regret it, as men we cannot but thank heaven that its whole generation is probably extinct.

coloured rays being thereby difposed to be tranfmitted through the plate, and confequently rays of different colours being difpofed to be reflected at the fame place, fo as to present the appearance of different colours to the eye.

A variation in the denfity of the plate, he fhows, will occafion a variation in the colour; but ftill a medium of any denfity would exhibit all the colours according to the thickness of the different parts of it. 'T'hefe obfervations he confirmed by experiments on plates of air, water, and glass. He alfo mentions the colours which arife on polished steel, by heating it; as likewife on bell-metal, and fome other metalline fubftances, when melted and poured on the ground, where they may cool in the open air and he afcribes these colours to the scoria, or vitrified parts of the metal, which, he fays, moft metals, when heated, or melted, do continually protrude, and send out to their furface, covering them in the form of a thin glaffy skin.

:

This capital discovery, concerning the colours of bodies depending upon the thickness of the fine plates, which compofe their furfaces, of whatever denfity thofe plates be (and which may be of fuch admirable ufe to explain the colours, and perhaps, in due time, the constituent parts and internal ftructure of natural bodies) I have been fo happy as to hit upon a method of illuftrating and confirming, by means of electrical explofions. Thefe, being received upon the furfaces of all the metals, change the colour of them, to a confiderable distance round the spot on which they are difcharged, fo that the whole space is divided into 5

a number of concentric circular fpaces, each exhibiting all the prifmatic colours; and perhaps as vivid as they can be made in any method

whatever.

It was not by any reafoning a priori, but by a mere accident, that I firft difcovered thefe colours. Having occafion to take a number of explofions, in order to ascertain the lateral force of them; I obferved that a plate of brafs, on which they were received, was not only melted, and marked with a circle, by a fufion round the central spot, but likewife tinged, beyond this circular fpot, with a green colour, which I could not eafily wipe out with my finger. Struck with this new appearance, I replaced the apparatus, and continued the explo-' fions; till, by degrees, I perceived a circle of red beyond the fainter colours; and, examining the whole with a microscope, I plainly diftinguished all the prifmatic colours, in the order of the rainbow. The diameter of the red, in this inftance, happened to be one third of an inch, and the diameter of the purple about one fourth.

Pleafed with this experiment, I afterwards purfued and diverfified it in a great variety of ways, the refult of which I fhall comprise in the following obfervations.

1. When a pointed piece of metal is fixed oppofite to a plain furface, the nearer it is placed to the furface, the fooner do the colours appear, the clofer do the rings fuc ceed one another, and the less space they occupy; as, on the other hand, the farther it is placed from the furface, the later do the colours appear; but the rings then occupy a proportionably greater fpace, and have more room to expand them

felves

felves. N° 1. on the fteel*, was made by the explofions paffing from the point of a needle, fixed at the diftance of of an inch from the steel; and N° 2. was made at the fame time, when the needle was placed at the diftance of of an inch. It feems, however, that when the point is placed at fuch a diftance, as that the electric matter has room to dilate, and form as large a circular spot as the battery` will admit, the rings are as large as they are capable of being made; but that ftill the colours appear later, in proportion to the distance beyond that. When the point is fixed exceeding near, or is made to touch the furface, the colours appear at the very firft explosion, but they spread irregularly, and make not diftinct rings, as N° 1. upon the tin.

2. The more acutely pointed is the wire, or needle, from which the electric matter iffues, or at which it enters, the greater number of rings appear. A blunt point makes the rings larger, but fewer; and in that circumftance it is likewife much later before the colours make their appearance at a given distance. N° 3. upon the fteel, was made by a blunt wire, and N° 2. upon the tin by a brass knob fixed oppofite to it.

3. In making these rings, the first appearance is a dufky red, about the edges of the circular spot; prefently after which (generally after four or five ftrokes) there appears a circular Space, vifible only in a pofition oblique to the light, and looking like a fhade on the metal. This space expands very little du

ring the whole courfe of the explofions, and it feems to be, as it were, an attempt at the first and faintest red; for by degrees, as the other colours fill the bulk of that space, the edges of this shade deepen into a kind of brown; as may be feen particularly in N° 4. upon the fteel, where it is fomething more than half an inch in diameter, and in N° 1. where it is near of an inch.

4. After a few more explosions, a fecond circular space is markedout by another fhade, beyond the firft, generally about or of an inch in diameter, which I have never obferved to change its appearance, after ever fo many explotions. This fecond fhade, by fucceeding the firft; which as I obferved, becomes gradually of a brown, or a light red, feems to be an attempt at the fainter colours, which intervene between the reds.

5. All the ftronger colours make their firft appearance at the edges of the circular fpot; and more explosions make them continually expand towards the extremity of the space first marked out, while others fucceed in their place; till, after about thirty or forty explosions, three diftinct rings generally appear, as in N° 4. upon the fteel. If the explosions be continued farther, the circle becomes lefs beautiful, and lefs diftinct; the red commonly prevailing, and fuffufing all the other colours, as in N° 1. upon the fteel; though I attribute the confufion of the colours in that circle, in part, to the needle having been several times accidentally broken from the cement which fupported