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cession of weight at the end of the first year, and were then carefully closed up again, were emaciated and dead before the expiration of the second year. .

At the same time that these toads were enclosed in stone, four other toads of middling size were enclosed in three holes cut for this purpose, on the north side of the trunk of an apple tree; two being placed in the largest cell, and each of the others in a single cell; the cells were nearly circular, about five inches deep and three inches in diameter ; they were carefully closed up with a plug of wood, so as to exclude access of insects, and apparently were air-tight; when examined at the end of a year, every one of the toads was dead and their bodies were decayed.

From the fatal result of the experiments made in the small cells cut in the apple tree, and the block of compact sandstone, it seems to follow that toads cannot live a year excluded totally from atmospheric air; and from the experiments in the larger cells within the block of colite limestone, it seems probable that they cannot survive two years entirely excluded from food; we may therefore conclude, that there is a want of sufficiently mninute and accurate observation in those so frequently recorded cases, where toads are said to be found alive within blocks of stone and wood, in cavities that had no communication whatever with the external air. The fact of my two toads having increased in weight at the end of a year, notwithstanding the care that was taken to enclose them perfectly by a luting of clay, shews how very small an aperture will admit minute insects sufficient to maintain life. In the cell No. 5, where the glass was slightly cracked, the communication though small was obvious; but, in the cell No. 9, where the glass cover remained entire, and where it appears certain, from the increased weight of the enclosed animal, that insects must have found admission, we have an example of these minute animals finding their way into a cell, to which great care had been taken to prevent any possibility of

access.

Admitting, then, that toads are occasionally found in cavities of wood and stone, with which there is no communication sufficiently large to allow the ingress and egress of the animal enclosed in them, we may, I think, find a solution of such phenomena in the habits of these reptiles, and of the insects which form their food. The first effort of the young toad, as soon as it has left its tadpole state and emerged from the water, is to seek shelter in holes and crevices of rocks and trees. An individual, which, when young, may have thus entered a cavity by some very narrow aperture, would find abundance of food by catching insects, which like itself seek shelter within such cavities, and may soon have increased so much in bulk as to render it impossible to go out again, through the narrow aperture at which it entered. A small hole of this kind is very likely to be overlooked by common workmen, who are the only people whose operations on stone and wood disclose cavities in the interior of such substances. In the case of toads, snakes, and lizards, that occasionally issue from stones that are broken in a quarry, or in sinking wells, and sometimes even from strata of coal at the bottom of a coal mine, the evidence is never perfect to shew that the reptiles were entirely enclosed in a solid rock; no examination is ever made until the reptile is first discovered by the breaking of the mass in which it was contained, and then it is too late to ascertain without carefully replacing every fragment (and in no case that I have seen reported has this ever been done) whether or not there was any hole or crevice by which the animal

may have entered the cavity from which it was extracted. Without previous examination it is almost impossible to prove that there was no such communication. In the case of rocks near the surface of the earth, and in stone quarries, .reptiles find ready admission to holes and fissures. We have a notorious example of this kind in the lizard found in a chalk pit, and brought alive to the late Dr Clarke. In the case also of wells and coal pits, a reptile that had fallen down the well or shaft, and survived its fall, would seek its natural retreat in the first hole or crevice it could find, and the miner dislodging it from this cavity to which his previous attention had not been called, might in ignorance conclude that the animal was coeval with the stone from which he had extracted it.

It remains only to consider the case, (of which I know not any authenticated example), of toads that have been said to be found in cavities within blocks of limestone to which, on careful examination, no access whatever could be discovered, and where the animal was absolutely and entirely closed up with stone. Should any such case ever have existed, it is probable that the communication between this cavity and the external

xtend two years

surface had been closed up by stalactitie incrustation after the animal had become too large to make its escape. A similar explanation may be offered of the much more probable case of a live toad being entirely surrounded with solid wood. In each case the animal would have continued to increase in bulk so long as the smallest aperture remained by which air and insects could find admission; it would probably become torpid as soon as this aperture was entirely closed by the accumulation of stalactite or the growth of wood; but it still remains to be ascertained how long this state of torpor may continue under total exclusion from food, and from external air: and although the experiments above recorded shew that life did not in the case of any one of the individuals which formed the subjects of them, yet, for reasons which have been specified, they are not decisive to shew that a state of torpor, or suspended animation, may not be endured for a much longer time by toads that are healthy and well fed up, to the moment when they are finally cut off from food, and from all direct access to atmospheric air.

The common experiment of burying a toad in a flower-pot covered with a tile, is of no value, unless the cover be carefully luted to the pot, and the hole at the bottom of the pot also closed, so as to exclude all possible access of air, earthworms and insects. I have heard of two or three experiments of this kind, in which these precautions have not been taken, and in which, at the end of a year, the toads have been found alive and well.

Besides the toads enclosed in stone and wood, four others were placed each in a small basin of plaster of Paris, four inches deep and five inches in diameter, having a cover of the same material carefully luted round with clay; these were buried at the same time and in the same place with the blocks of stone, and on being examined at the same time with them in December, 1826, two of the toads were dead, the other two alive, but much emaciated. We can only collect from this experiment, that a thin plate of plaster of Paris is permeable to air in a sufficient degree to maintain the life of a toad for thirteen months.

In the 19th Vol. No. 1, p. 167, of Silliman's American Journal of Science and Arts, David Thomas, Esq. has published some observations on frogs and toads in stone and solid earth, enu32 On the Vitality of Toads enclosed in Stone and Wood. merating several authentic and well attested cases; these, however, amount to no more than a repetition of the facts so often stated and admitted to be true, viz. that torpid reptiles occur in cavities of stone, and at the depth of many feet in soil and earth ; but, they state not any thing to disprove the possibility of a small aperture, by which these cavities may have had communication with the external surface, and insects have been admitted.

The attention of the discoverer is always directed more to the toad than to the minutiæ of the state of the cavity in which it was contained.

In the Literary Gazette of March 12. 1831, p. 169, there is a very interesting account of the habits of a tame male toad, that was domesticated and carefully observed during almost two years by Mr F. C. Husenbeth. During two winters, from November to March, he ate no food, though he did not become torpid, but grew thin and moved much less than at other times. During the winter of 1828, he gradually lost his appetite and gradually recovered it. He was well fed during two summers, and after the end of the second winter, on the 29th of March, 1829, he was found dead. His death was apparently caused by an unusually long continuance of severe weather, which seemed to exhaust him before his natural appetite returned. He could not have died from starvation, for the day before his death he refused a lively fly.

Dr Townson also, in his tracts on Natural History, (London 1799), records a series of observations which he made on tame frogs, and also on some toads; these were directed chiefly to the very absorbent power of the skin of these reptiles, and show that they take in and reject liquids, through their skin alone, by a rapid process of absorption and evaporation,—a frog absorbing sometimes in half an hour as much as half its own weight, and in a few hours the whole of its own weight of water, and nearly as rapidly giving it off when placed in any position that is warm and removed from moisture. Dr T. contends that as the frog tribe never drink water, this fluid must be supplied by means of absorption through the skin. Both frogs and toads have a large bladder, which is often found full of water ; “ whatever this fluid may be, (he says), it is as pure as distilled water and equally tasteless; this I assert as well of that of the toad which I have often tasted, as that of frogs.”

4

On the Chemical Constitution of Harmotome, or Cross-stone.

By Arthur Connell, Esq., F.R.S.E. Communicated by

the Author *. In examining some specimens of harmotome from Strontian, I observed some crystals which appeared to present a very

different aspect from the ordinary barmotome with which they were associated. The usual crystals of this mineral from the above locality are well known to be of considerable size, and to exhibit the form of a rectangular prism, Plate I. Fig. 1, terminated by a pyramid, the faces of which are set on the lateral edges of the prism, two opposite edges of the pyramid being also replaced by planes. On the other hand, the crystals to which I have referred were a great deal smaller in size, usually not exceeding one-tenth of an inch in length, and of greater transparency ; and they presented the apparently very dissimilar form of a rhombic prism, Fig. 3, of considerable acuteness, having the acute angle more or less truncated by the face A, and terminated by a pyramid C, the faces of which were set on the lateral planes of the prism, and its apex truncated. They were spread over the surface of calcareous spar in considerable numbers, and were usually attached to the matrix by one of the extremities D D. Farther consideration, however, showed that this latter form was in reality merely a modification, although undoubtedly a very considerable one, of the old form, and arose principally from the vertical contraction of the crystal, Fig. 1, and its horizontal elongation in the direction of the faces BB', the inclination of the several faces to one another remaining always the same; as will be evident by comparing Figures 1, 2, and 3, Fig. 2 representing another form of the crystal, which may be regarded as intermediate between Figs. 1 and 3, and the whole three being placed in parallel position, with their corresponding faces marked by the same letters. In some rare instances, the pyramids CC, and the face A, Fig. 3, almost entirely disappear, so that the crystal appears nearly as a simple rhombic prism; and in others equally rare, the face D almost disappears, so as to leave the pyramid nearly without truncation.

* Read to the Royal Society of Edinburgh, 2d April 1832. VOL. XIII. NO, XXV.-JULY 1832.

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