of death. This fact is almost all that is neceffary to explain the lu minous appearance in the eyes of cats." P. 3.

Having found the retina to be perfectly tranfparent, when the eye is examined in a very recent ftate, Mr. H. was led to fufpect, that the internal part of the optic nerve, when examined in the fame ftate, might alfo be tranfparent; and, for the purpose of determining this matter, made the following experiment:

"The pofterior half of a cat's eye, while in a very recent state, was immerfed in a bafon of water, and examined. The tapetum ap peared very bright, the retina not having acquired fufficient opacity to become vifible. The entrance of the optic nerve was a very white fpot, which feemed to be opaque; but, when small pieces of coloured paper were alternately placed between the outfide of the eye and the bottom of the bafon, their colour was diftinctly seen in the cavity of the eye, through the fubftance of the optic nerve; fo that, at this part, the internal ftructure of the nerve has a degree of transparency." P. 6.

After having afcertained the femi-tranfparent nature of the internal parts of the recent optic nerve, Mr. H. was induced to examine its fubftance, by means of magnifying glaffes. But, previous to the account of his own experiments, he gives a fhort view of the principal theories concerning the structure of nerves, that have been advanced by other philofophers, namely, Torre, Prochaska, Fontana, and Dr. Monro,

The microscope ufed by Mr. H. in thefe experiments, was a fingle lens, that magnified the object about twenty-three times; and the objects were attentively viewed both by himfelf and by Mr. Ramfden. The experiments were made, with all due care and attention, both on transverse and on longitudinal fections of the optive nerve of the horfe, recently dead. The refult is as follows:

"At its origin from the brain, it confifts of 30 or 40 fafciculi or bundles of extremely fmall opaque pulpy fibres, the interstices between which are filled with tranfparent jelly. As the nerve goes farther from the brain, the fafciculi form fmaller ones, of different fizes, This is not done by a regular fubdivifion, but by a few fibres going off laterally from feveral large fafciculi, and being united, forming a maller one. Some of the fafciculi fo formed, which are very small, unite again into one. In this way the fafciculi gradually diminish in fize, and increase in number, till they terminate in the retina.

"Near the eye, where the fafciculi are most numerous, the fubftance of the nerve has a confiderable degree of transparency, from the number of transparent interstices between them; but this is lefs the cafe nearer the brain, where the interstices are fewer.

"In the optic nerve of the cat, the ftructure is the fame as in the horfe; but, from the fmallness of the parts, less fitted for investigation.

A 2.

Near

Near the eye, its internal fubftance is more tranfparent than the correfponding part in the herfe."

To fee how far this ftructure was peculiar to the optic nerve, fimilar experiments were made upon the internal fubitance of the fifth and feventh pair of nerves, near the origin at the brain, and the ftruc. ture was found to be the fame. In thefe laft-mentioned nerves, the.. interftices between the fafciculi were fmaller than in the optic nerve,: rendering their tranfverfe lections lefs tranfparent; from which, it is natural to fuppofe that the internal parts of the optic nerve are not fo compact as in other nerves, and therefore it is better fitted for examination.

"Thefe experiments fhow, that the nerves do not confist of tubes conveying a fluid, but of fibres of a peculiar kind, different from every thing elfe in the body, with which we are acquainted. The courfe of thefe fibres is very curious; they appear to be conftantly paffing from one fafciculus to another, fo as to connect all the different fafciculi together by a mixture of fibres. This is different from the courfe of blood veffels, lymphatics, or mufcular fibres: the only thing fimilar to it, is in the formation of nervous plexufes; which leads to the idea of its anfwering an effential purpose, refpecting the functions of the nerves." P. 11.

II. The Bakerian Lecture. Obfervations upon an unusual horizontal Refraction of the Air; with Remarks on the Variations to which the lower Parts of the Atmosphere are fametimes Subject. By the Rev. S. Vince, A. M. F.R. S. and Plumian Profeffor of Aftronomy and Experimental Philofophy in the University of Cambridge. P. 13.

The author of this paper defcribes, and endeavours to explain, a fingular effect of horizontal refraction, obferved by himfelf at Ramfgate, on the 1st of Auguft laft. The observations were made through a telescope that magnified between 30 and 40 times; though the phænomenon was visible to the naked

eye.

When the mafts of a ship were just seen above the horizon of the fea, there appeared at the fame time in the field of view' of the telescope, two complete images of the fhip in the air, vertical to the ship itfelf. One of thofe images was inverted, and the other erect, having their hulks joined.

Similar double images were alfo feen of other objects; but we are unable to give our readers a more adequate idea of this unufual phænomenon, as also of its explanation, without the affiftance of the plate which accompanies the paper itself.

III. Abstract of a Register of the Barometer, Thermometer, and Rain, at Lyndon, in Rutland, 1797. With Some Remarks on the Recovery of injured Trees. By Thomas Barker, Efq. P. 24.

This Register gives the highest, the lowest, and the mean height of the barometer, and of the thermometer, both within and without the houfe; together with the quantity of rain, for every month throughout the year 1797. The rain, upon the whole, amounts to 27,854 inches. This Regifter, which occupies only one page, is followed by fome general remarks on the peculiar nature of the feafons, the produce of the ground, &c.

With respect to the recovery of injured trees, Mr. Barker relates two cafes of young oak-trees, that having been broken by accident, the upper parts were cut off; but, as the part that had remained in the ground put out fhoots, he trained up the best shoot of each tree, which, after a certain time, appeared likely to become good trees.

IV. Same Additions to a Paper, read in 1790, on the Subject of a Child with a double Head. By Everard Home, Efq. F. R. S. P. 28..

In the 80th volume of the Philofophical Tranfactions there is a paper of the fame author, giving an account of a child with a double head. The child had been born in India, where he died when he was upwards of four years old; his double fkuli was fent to England, and was exhibited at a meeting of the Royal Society. Mr. Dent, the gentleman who had tranfmitted the above-mentioned fkull from India, returning not long ago to England, furnished Mr. Home with further particulars relative to the double headed child, and likewife with two portraits of him; namely, a front view and a profile of the dou ble head, taken whilft the child was living, by a Mr. Devis, an artist of confiderable merit. Two copper-plate engravings of the portraits are annexed to the paper. The additional remarks, which were furnished by Mr. Dent, are as follows: The child was a male.

The mother had had three other children naturally formed. She could affign no imaginary or accidental caufe during her pregnancy, that might have been productive of the monitrous child.

The body of the child was uncommonly thin.

"The neck of the fuperior head was about four inches long; and the upper part of it terminated in a hard, round, griftly tumour, nearly 4 inches in diameter.

« The front teeth had cut the gums in the upper and lower jaw of both heads.

When the child cried, the features of the fuperior head were not always affected; and when it fmiled, the features of the fuperior head did not fympathize in that action,

"The

"The dura mater belonging to each brain was continued acrofs, at the part where the two fkulls joined, so that each brain was invested in the ufual way, by its own proper coverings; but the dura mater, which covered the cerebrum of the upper brain, adhered firmly to the dura mater of the lower brain," P. 30.

A number of large arteries and veins were found paffing through the union of the dura matres; it was therefore through those blood-veffels that the upper brain received its nourishment.

V. Obfervations on the Manners, Habits, and Natural Hif tory of the Elephant. By John Corfe, Efq. P. 31.

It is a matter of wonder, that though elephants have been long fought after, employed, and admired, on account of their fize, fagacity, and docility, yet the knowledge of their œconomy, manners, &c. has been always involved in mystery and doubt, A refidence of upwards of ten years in Tiperah, a province of Bengal, where herds of elephants are caught every feafon, afforded the writer of this paper opportunities fufficient to afcertain several interefting particulars, and enabled him to contradict many vulgar errors relative to thofe animals.

It has been repeatedly afferted, that elephants poffefs the sentiments of modefty in a high degree; and that they are fo much affected by the lofs of their liberty, as to refuse to propagate the fpecies whilft they remain in a ftate of captivity.

The ufual fize of those animals has likewife been much exaggerated.

It has been afferted, as an inftance of their great fagacity, and retentive memory, that if an elephant once escapes, it is not poffible to catch him again by any art.

Mr. Corfe's observations contradict thofe vulgar notions; he reduces their size to the real standard, and ascertains feveral other particulars relative to these animals. We fhall endeavour to condense the most remarkable particulars into the following paragraphs:

Several elephants, to Mr. Corfe's certain knowledge, after having effected their efcape, have been retaken, and often in a very easy manner.

In India, the height of female elephants is, in general, from feven to eight feet, and that of males from eight to ten, meafured at the fhoulder. One elephant only, amongst those that came within Mr. Corfe's knowledge, exceeded the height of ten feet. The dimenfions of this elephant were as follows:

"From

Feet. Inches.

22

10

191 6

12 2

"From foot to foot over the fhoulder From the top of the fhoulder, perpendicular height. From the top of the head, when fet up, as he ought to march in state From the front of the face to the infertion of the tail 15 11.". Tame elephants copulate without hefitation, provided the females are in a proper itate; and Mr. Corfe, belides a great many other perfons, has been repeatedly fpectator of the fact. The females begin to give evident figns of impregnation within about three months from the time of their having been covered. Their ufual time of gestation feems to be about 21 months, or 20 months and 18 days.

The elephant, at the time of its birth, feldom exceeds the height of thirty-four inches; and they generally obtain their full fize between the age of eighteen and twenty-four years.

The young elephants begin to nibble, and fuck the breast foon after birth.

"Tame elephants," fays Mr. Corfe," are never fuffered to remain loofe; as inftances occur of the mother leaving even her young, and efcaping into the woods.

"Another circumftance deferves notice: if a wild elephant happens to be feparated from her young, for only two days, though giving fuck, fhe never afterwards recognizes or acknowledges it. This feparation fometimes happened unavoidably, when they were enticed feparately into the outlet of the Keddah. I have been much mortified at fuch unnatural conduct in the mother; particularly when it was evident the young elephant knew its dam, and, by its plaintive cries and fubmiffive approaches, folicited her affiftance."

VI. On the Decompofition of the Acid of Borax or fedative Salt. By Lawrence de Crell, M. D. F. R. S. &c. P. 56. The acid called fedative falt, is one of the conftituent principles of a well-known natural production, called borax, and is fparingly, or feldom, found in any other fubftance.

Numerous, but ineffectual, experiments have been inftituted by different chemifts, for the purpofe of forming this falt by compofition; nor had a decompofition of the fedative falt been effected by any perfon, when Dr. de Crell began his experiments; which, indeed, can hardly be wondered at, if it be confidered that this falt may be kept fluid in a very hot fire, until it becomes a vitrified substance, without loofing its effential properties.

Dr. de Crell began, by confidering in what manner the decompofition of this falt might be effected, and, after due confideration, he attempted it by means of oxygenated muriatic acid, and of a gentle heat, long continued, which, as experience had fhown, is more efficacious in difficult decompofitions than a violent heat.

He