EXPLANATION OF THE plates.

(See Plates XVI, XVII, XVIII, XIX, XX, XXI, XXII.)

Six of the following Plates are taken from drawings made by Mr. HOWSHIP, who very kindly undertook that task, during the indisposition of Mr. CLIFT, and his knowledge of anatomy, which he has cultivated with much ardour, induced me to solicit his assistance upon this occasion.

PLATE XVI.

Fig. 1. A view of the pectoral fin of the Squalus Maximus, from which the skin and cellular membrane are removed, to shew the arrangement of the cartilages of which it is composed.

Fig. 2. A portion of the elastic fibrous structure with which the fin is tipped, of its natural size.

PLATE XVII.

Fig. 1. An internal view of the stomach and duodenum of the Squalus Maximus.

a. The oesophagus.

bb. The cardiac portion of the stomach.

cc. The pyloric portion.

dd. The spleen.

e. A small cavity belonging to the stomach.

ff. The duodenum.

g. The band containing the hepatic ducts, six in number.

h. The dilatation in which the gali ducts terminate.

i. The opening of the pancreatic duct.

k. The spiral turns of the intestine.

Fig. 2. The fringe at the termination of the oesophagus of the natural size.

PLATE XVIII.

The heart of the Squalus Maximus laid open.

aa. A portion of the internal surface of the auricle.

bb. One of the venæ cave laid open.

c. The valve between the auricle and ventricle.

dd. The cavity of the ventricle.

eee. The three rows of valves and the three intermediate spaces, along which regurgitation takes place when the canal of the artery is dilated.

ff. The strong muscular covering of the artery.

PLATE XIX.

A side view of the cerebellum, tubercula quadrigemina, and nerves of the brain of the Squalus Maximus.

3, 4, 5, 6, 7, 8. The different nerves going off from the brain corresponding with those in the brain of man.

a. Cerebellum.

bb. Two of the tubercula quadrigemina.

c. A third tuberculum mutilated.

PLATE XX.

A view of the upper surface of the cerebellum and nerves of the Squalus Maximus.

The nerves going off marked, as in the last Plate, beyond which are two pair of nerves belonging to the spinal marrow.

aa. Cerebellum.

bb. Two of the tubercula quadrigemina.

cc. The part which corresponds with the fourth ventricle in the human brain, surrounded by an oval, continued, nervous band, from which the principal nerves go off.

ddd. Portions of the three semicircular canals of the ear in the cartilaginous cavity in which they are contained.

PLATE XXI.

A view of the upper surface of the brain of the Squalus Acanthias, taken from a fish three feet long, to shew the difference of appearance and size between it and that of the Squalus Maximus.

The brain is entire, and the eyes are left in their situation, so that when this Plate is compared with that of the large brain, the parts that are wanting in it will be readily distinguished.

PLATE XXII.

A view of the heart of the Lophius Piscatorius in a distended state, shewing the transparency of its coats, which are extremely thin.

a. The auricle.

b. The ventricle.

c. The branchial artery.

d. The projecting muscular tube serving as a valve.

XXVIII. Some further Observations on a new detonating Substance. In a Letter from Sir Humphry Davy, LL.D. F.R. S. V. P. R. I. to the Right Hon. Sir Joseph Banks, Bart. K. B. P. R.S.

I

MY DEAR SIR,

Read July 1, 1813.

Berkeley-square, June 20, 1813.

HAVE already described, in a letter which you were so good as to communicate to the Royal Society, a few facts respecting a new detonating compound. I shall now do myself the honour of inentioning to you some other particulars on the subject.

I received, in April, a duplicate of the letter in which the discovery was announced, containing an Appendix, in which the method of preparing it was described. M. AMPERE, my correspondent, states that the author obtained it by passing a mixture of azote and chlorine through aqueous solutions of sulphate, or muriate of ammonia. It is obvious, from this statement, that the substance discovered in France, is the same as that which occasioned my accident. The azote cannot be necessary; for the result is obtained by the exposure of pure chlorine to any common ammoniacal salt.

Since I recovered the use of my eyes, I have made many experiments on this compound; it is probable that most of them have been made before in France; but as no accounts of the investigations of M. DULONG on the substance have

appeared in any of the foreign journals which have reached this country, and as some difference of opinion and doubts exist respecting its composition, I conceive a few details on its properties and nature will not be entirely devoid of interest.

I have been able to determine its specific gravity, I hope, with tolerable precision, by comparing its weight at 61° FAHRENHEIT, with that of an equal volume of water. 8,6 grains of the compound, carefully freed from the saline solution in which it was produced, filled a space equal to that filled by 5,2 grains of water, consequently its specific gravity is 1,653.

When the compound is cooled artificially, either in water or in solution of nitrate of ammonia, the fluid surrounding it congeals at a temperature a little below 40° Fahrenheit, which seems to be owing to its becoming a solution of chlorine; for, as I have stated in a paper published in the Philosophical Transactions, the saturated solution of chlorine in water freezes very readily. The congelation of the fluid, in contact with the new compound, led me, when I first operated on it in very small quantities, to suppose it readily rendered solid by cooling; but I find in experimenting upon it, out of the contact of water, that it is not frozen by exposure to a mixture of ice and muriate of lime.

The compound gradually disappears in water, producing azote, and the water becomes acid, and has the taste and smell of a weak solution of nitro-muriatic acid.

The compound, when introduced into concentrated solution of muriatic acid, quickly resolves itself into gas, producing much more than its own weight of elastic fluid, which proves to be pure chlorine, and the solution evaporated affords muriate of ammonia.