« ПредишнаНапред »
survey of Clare Island, on the west coast of Ireland, illustrating the same by maps and sections executed by Mr Bald.
The Professor then gave a general descriptive account of a splendid series of the Pheasants and Peacocks of India, specimens of which were placed on the table. A stuffed specimen of a Persian Sheep, presented to the Royal Museum by James Gibson Craig, Esq. was also exhibited. Mr Audubon laid before the meeting several specimens of the coloured Plates of his great work on American Ornithology, executed by Mr Lizars of this city; and they excited general admiration.
1. Repulsion of Heat inversely as the square of the distance. -Sir Isaac Newton has shewn, Principia, Lib. ii. Prop. 23*, that if the repulsion between the particles of a gas were inversely as the square of the distance of their centres, the cube of the pressure would be as the fourth power of the density, and vicc versa. Now this is precisely the relation which we formerly saw should subsist between the pressure and density of air containing a constant quantity of heat, if, as appears from experiment, the specific heat under a constant volume be to that under a constant pressure as 3 to 4†; and, therefore, whilst the quantity of heat connected with each particle of air is constant, the repulsion between them is inversely as the square of their distance. This being the law common to magnetism and gravitation, scarcely leaves a doubt that the true ratio is that of 3 to 4. It is also the actual law of gaseous repulsion; for that first given by Newton, and generally adopted, making the repulsion inversely as the simple distance, really compares the re
Some allege that this proposition requires each particle to act those next it; but it holds equally true, whilst each acts on a con ber, however great, if similarly situated.
+ See equation (C) page 336. vol. i. of this Journal
Any tendency in the particles to gravitate toward each other,
pulsions in cases where not only the distances, but the quantities of heat are different. The above principle of the repulsions, being inversely as the square of the distance, might easily be shewn to accord with the law of temperature and the law of Boyle. Any variation in the quantity of heat, will, cat. par., produce proportional variations in the logarithms of the repulsions. Perhaps the same property belongs to magnetism or electricity, if not to gravitation itself. HENRY MEIKLE,
2. The Beech-Tree a Nonconductor of Lightning.-Dr Beeton, in a letter to Dr Mitchill of New York, dated 19th July 1824, states, that the beech-tree (that is, the broad-leaved or American variety of Fagus sylvatica) is never known to be assailed by atmospheric electricity. So notorious, he says, is this fact, that, in Tenessee, it is considered almost an impossibility to be struck by lightning, if protection be sought under the branches of a beech-tree. Whenever the sky puts on a threatening aspect, and the thunder begins to roll, the Indians leave their pursuit, and betake themselves to the shelter of the nearest beech-tree, till the storm pass over; observation having taught these sagacious children of nature, that, while other trees are often shivered to splinters, the electric fluid is not attracted by the beech. Should further observation establish the fact of the nonconducting quality of the American beech, great advantage may evidently be derived from planting hedge-rows of such trees around the extensive barn-yards in which cattle are kept, and also in disposing groups and single trees in ornamental plantations in the neighbourhood of the dwelling-houses of the
3. Silica in Springs is dissolved by means of Carbonic Acid. -Dr Karsten remarks, that, if so feeble an acid as the acetous, is capable of dissolving silica, it is not improbable that the carbonic acid may have the same property. This conjecture he has confirmed by experiment. The experiment may be made as follows. Decompose a portion of liquor silicum by means of a superabundance of any acid, the muriatic, for example, and neutralize the clear fluid with carbonate of ammonia, at the lowest possible temperature. The carbonic acid evolved by this
process combines with the water; and, if the neutral fluid is preserved in a well-closed glass-vessel, it may be kept for many weeks, without exhibiting any precipitation of silica. But if it is exposed to the air, or, better, if the solution is heated in an . open vessel, it is decomposed in proportion to the escape of the carbonic acid, and the siliceous earth is deposited on the walls of the vessel in a gelatinous state. This result shews, that thè great quantity of silica met with in many mineral springs, particularly hot springs, is held in solution by carbonic acid. It is true, that we cannot in this way explain how the siliceous earth was first dissolved,-for the generally received opinion, that the earth is simply washed cut of the strata in the vicinity of the springs, is, according to Karsten, untenable.
4. Tit-Lark caught at Sea.-I have, at this moment, be fore me (says Dr Traill of Liverpool) extracts from the journal of my intelligent friend Captain Andrew Livingston, which, among other things, notices, that a small bird alighted on the brig Jane of this port, in Lat. 47° 4' South, Long. 43°19′ West, on September 11. 1825. It was caught, and when examined here, proved to be the common tit-lark (Alauda pratensis.)`
5. Egyptian Antiquities in Liverpool Museum.We have in our Museum, many fine Egyptian antiquities; among these is a beautiful papyrus, found in the hand of a mummy. It is upwards of 20 feet in length, the hieroglyphics beautifully executed, and interspersed with numerous pictures. One of these is a representation of the Egyptian Last Judgment, as described by Diodorus Siculus; in which the spirit of the deceased is ushered by a genius before the god Thoth, who sits with his tablets writing down the result of a trial, then before him, in which the deeds of the deceased are weighed in a balance, the vibrations of which are intently watched by Cerberus. In an upper compartment, the happy issue of the trial is announced "by the introduction of the human spirit, under the guidance of the same genius, to Osiris. We have an unrolled head of a mummy, a young female, with high thin nose, and long auburn ringlets, confirming the opinion of Cuvier, Blumenbach, and others, that the Egyptians (of the era, at least, of this mum
my) were not Negroes. We have also several mummies shoes, and a beautiful sandal of plaited palm leaves, all which are made" right and left," so that even this modern fashion has had an Egyptian origin. I have, in my possession, several Egyptian antiquities, among the rest an exquisite bronze figure of Harpocrates, with his finger on his lips, and the sacred beetle on his head. The contour of the body, and grace of the head, are quite Grecian.-Letter from Dr Traill.
6. Notice regarding the Common Star-Fish, Asterias rubens. On the 6th of March last year, M. Eudes Deslongchamps observed the beach at Colville to be covered with starfish. When the waves retired, and there was still an inch or two of water upon the sand, he saw them rolling out in the form of balls, which, on examination, he found to consist of five' or six individuals, closely united and clinging together by their rays. In the centre of each of these balls was a full grown specimen of Mactra stultorum. The asteriæ were arranged along the edge of the valves, which were always separated to the distance of two or three lines; they were applied to them by their lower surface. On detaching them from the shell, it was remarked, that they had introduced between its valves, large round vesicles, with very thin walls, and filled with a transparent fluid. Each asterias presented five pendent vesicles, arranged symmetrically about the mouth. These vesicles were of unequal size: two of them were commonly larger, and about the size of a very large hazel-nut; the other three were not larger than a pea. They appear to be connected with the animal by a very short and narrow peduncle. At the other extremity was a round open hole, through which the fluid, contained in the vesicle, flowed gently, and drop by drop. The walls of these vesicles were very thin; the upper half, however, was thicker than the other and longitudinally wrinkled. At the end of a few seconds, the vesicles having contracted and discharged their contents, were scarcely larger than a grain of ordinary shot. When the sea had left the asteriæ some moments dry, they quitted the animal which they were in the act of sucking, and immediately after, the place of the vesicles could no longer be distinguished. The shells, that had been seized
upon by these animals, were found in various states of destruction; some so far gone as to have only the adductor muscles remaining; but all of them had lost the faculty of closing their valves, and appeared to be dead. If testacea be the ordinary food of the asteriæ, an enormous quantity of them must be destroyed, if we may judge by the number of these animals. M. Deslongchamps inclines to the opinion that the asteriæ attack the mactræ while the latter are still alive, and that, probably, by means of some fluid, capable of producing torpor, they force them to open their shells, and thus allow the introduction of the singular bodies described, and which act as suckers. He is the more inclined to think so, that none of the mactræ, which he examined, had the least smell, or presented any other indication of having been dead for any time. must, however, be remembered, that bivalve shells of this, or any other analogous species, tossed about by the waves, are no longer in their natural state, but have been raised from their native haunts under the sand, either by boisterous weather, or after intense frost, by even a scarcely more than ordinarily troubled state of the sea. Shells in this state are frequently observed on our shores. In some the animals are dead, in others so much weakened, as to be unable to close their shells, while others may, at least after gales, be for a time apparently as sound as ever. Now, it is more than probable, that the asteriæ could only attack those which were absolutely dead or dying, and from which the insertion of their suckers could experience no opposition; for it would be impossible for them to insinuate even a pretty solid substance, much less a mere vesicle, between the closed valves of a living shell; and, on the other hand, how should the asteriæ contrive to make the shell of a vigorous animal open, in order to let them throw in their imagined torporiferous fluid ?
7. Conclusions of M. Dureau de la Malle's Inquiries, respecting the Ancient History, Origin, and Native Country of the Cereales, and especially Wheat (Triticum hibernum and æstivum), and Barley (Hordeum vulgare and hexastichon).—