distilled almost without decomposition. Vanadium oxytribromide dissolves in water, yielding a yellow-coloured solution, in which both vanadium and bromine were determined, after reduction with sulphurous acid :

The specific gravity of the oxytribromide at 0° is 2.967.

3. Vanadium Oxydibromide, or Vanadyl Dibromide, VOBr2, molec. wt. 227.3.-This is a solid substance, of a yellowish-brown colour, obtained by the sudden decomposition of the foregoing compound at temperatures above 100°, or by its slow decomposition at the ordinary temperature.

The oxydibromide is very deliquescent, dissolving in water, with formation of a blue solution of a vanadious salt. When heated in the air it loses all its bromine, and is converted into V, O,.

Iodine-vapour does not attack either the trioxide or the nitride at red heat; both these substances remain unchanged, and no trace of vanadium can be detected in the iodine which has passed over them.

IV. THE METALLIC VANADATES.

In the first part of these Researches (Phil. Trans. 1868) it was pointed out (1) that the salts analyzed by Berzelius must be considered as meta- or monobasic vanadates, (2) that the so-called bivanadates analyzed by Von Hauer are anhydro-salts, and (3) that the ortho- or tribasic vanadates contain 3 atoms of monad metal, the sodium salt being formed artificially by fusing 1 molecule of vanadium pentoxide with 3 molecules of carbonate of soda, when 3 molecules of carbon dioxide are expelled, whilst the orthosalts occur native in many minerals. The present communication contains a description of these classes of salts, as well as of a new class of salts, the tetrabasic or pyro-vanadates.

Sodium Vanadates.

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1. Ortho- or Tri-Sodium Vanadate, Na, VO, +16H, O,.-When a mixture of 3 molecules of Na, CO, and 1 molecule of V, O, is fused until no

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further evolution of CO, is observed, a tribasic vanadate remains as a white crystalline mass. This mass dissolves easily in water, and on addition of absolute alcohol to the solution two layers of liquid are formed; the lower one solidifies after a time, forming an aggregation of needle-shaped crystals, which possess a strongly alkaline reaction. These having been washed with alcohol, and dried on a porous plate over sulphuric acid in vacuô, were analyzed with the following results :

The sodium in this and in the following compounds was separated from the vanadium by precipitating the vanadic acid as the perfectly insoluble basic lead salt hereafter described. This was dried at 100° and weighed, then dissolved in nitric acid and decomposed by sulphuric acid, and the solution of V, O, in excess of this acid gave on evaporation a finely crystalline mass. The filtrate from the lead precipitate freed from lead yielded on evaporation sodium sulphate. Full analytical details of this method, as well as of the other by precipitation as the insoluble ammonium metavanadate, are given in the memoir. By frequent crystallizations the trisodium vanadate is slowly decomposed into the tetrasodium salt, caustic soda being formed. This singular reaction was most carefully examined and the amount of sodium hydroxide liberated determined volumetrically. 2. Tetrasodium Vanadate, Na ̧ V2 O, +18H, O.—This salt crystallizes in beautiful six-sided tables; it is easily soluble in water, insoluble in alcohol, and is precipitated by the latter liquid from aqueous solution in white scales of a silky lustre. As long as the salt contains free alkali or tribasic salt, it forms, on precipitation with alcohol, oily drops which solidify after some time. The tetrasodium vanadate is always formed by the first fusion of vanadic acid with excess of carbonate of soda, and can be easily prepared in the pure state by recrystallization.

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The corresponding Calcium and Barium Vanadates, Ca V, O., and Ba, V, O,, are white precipitates obtained by adding the chlorides to a

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solution of tetrasodium vanadate. If calcium chloride be added to a solution of the trisodium salt, dicalcium vanadate is precipitated, the solution becoming strongly alkaline from formation of calcium hydroxide and absorbing carbonic acid from the air. Complete analysis showed that the calcium salt contains 2 molecules of water of crystallization, whilst the barium salt is anhydrous.

Lead Vanadates.

1. Tribasic or Ortho-Lead Vanadate, Pb, 2(VO,).—Obtained as a light yellow insoluble powder on precipitating the tribasic sodium salt with a soluble lead salt; it yielded on analysis 11.75 per cent. of vanadium, the calculated quantity being 12:04 per cent.

2. Vanadinite, the Double Orthovanadate and Chloride of Lead, 3Pb, VO1+Pb Cl2, can be artificially prepared by fusing for a few hours a mixture of vanadic acid, oxide of lead, and chloride of lead, in the above proportions, together with an excess of sodium chloride. After cooling, a greyish crystalline mass is left, containing cavities filled with long crystals having the same colour as the mass, which under the microscope could be distinguished as six-sided prisms. The crystalline powder is then boiled with water until no further traces of soluble chlorides are extracted.

The following analysis shows that this substance has the same composition as the vanadinites from Zimapan and Windischkappel, analyzed by Berzelius and Rammelsberg* :-

Natural vanadinite.

Calculated. Zimapan, Windischkappel, Artificial 3 (Pb, VO4) Pb Cl. Berzelius. Rammelsberg.

Vanadinite.

The specific gravity of the artificial vanadinite at 12° C. is 6.707, that

of the natural being 6-886.

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3. Basic Di-Lead Vanadate, 2(Pb, V, O,)+ Pb O.--This salt is precipitated as a pale yellow powder when acetate of lead is added to a solution. of disodium vanadate, the liquid acquiring an acid reaction. It is completely insoluble in water and in dilute acetic acid, but dissolves readily in nitric acid.

*Pyromorphite and apatite have already been artificially prepared by Deville and Caron, and also by Debray, whilst mimetesite has been obtained artificially by Lechartier.

Silver Vanadates.

1. The Ortho-Silver Vanadate, Ag, VO,, is obtained as an orange-coloured precipitate by mixing a freshly prepared solution of the trisodium salt with a solution of silver nitrate, in which every trace of free acid has been neutralized; unless these precautions are attended to, the precipitate consists of a mixture of the ortho- and pyro-salt. The trisilver vanadate is insoluble in water, but readily dissolves in ammonia and nitric acid. Analysis gave the following results :—

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2. The Tetrabasic Silver Vanadate, Ag, P, O,, is prepared by mixing a solution of the corresponding sodium salt with a neutral solution of nitrate of silver. It falls as a yellow dense crystalline precipitate, resembling in colour the ordinary phosphate of silver. On dissolving the salt in nitric acid, the silver is precipitated as chloride, and the vanadium determined as V2O,.

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Analysis gave:

The reactions of the tri- and tetrabasic vanadates of the other metals

are then described.

The author has to thank Messrs. Oelhofer and Finkelstein for the valuable assistance which they have given him in the above investigation.

The Society adjourned over the Easter Recess to Thursday, April 28.

April 28, 1870.

Dr. WILLIAM ALLEN MILLER, Treasurer and Vice-President, in the Chair.

Principal Dawson, LL.D., of M'Gill College, Montreal, was admitted into the Society.

The following communications were read :—

Re

I. "On the Organs of Vision in the Common Mole." By ROBERT JAMES LEE. Communicated by SAMUEL SOLLY, F.R.S. ceived March 30, 1870.

The eye of the Common Mole and the structures connected with it undergo some remarkable changes during the growth of the animal. The gentleman who does me the honour to present the results of an investigation into that subject to the Royal Society was desirous that it should be undertaken in order to ascertain the cause of the anomalous condition in which the organ of vision is found in the adult Mole.

It was the suggestion of Mr. Solly that an examination of the eye of the young or fœtal Mole might assist in the explanation; for Mr. Solly had reflected much on the subject, and entertained reasons for believing that such an inquiry would be attended with a satisfactory result.

It is known that there is distinct evidence of the existence of an eye and other parts concerned in the endowment of sight in many of the various species of the Mole genus. To what extent, however, the defective state of the organs permit of sight, or whether the animal is totally blind, are questions still undecided.

That the organs of vision in the young Mole would be found in a more perfect state than in mature age was what Mr. Solly anticipated, while he conjectured, for physiological reasons, that the cause of the difference between them would be found to be a process of atrophy or degeneration in the various structures essential for the enjoyment of sight.

The specimens sent me for the purpose of examination consisted of a female Mole, which appeared from its dimensions to have attained the full period of development, if it had not somewhat exceeded it, and of six unborn. young about an inch and a quarter long, and, as far as I could judge, beyond the middle of the period of gestation.

Before entering into anatomical details, I venture to review briefly the researches which have been made by anatomists into this subject. A summary of the views entertained by those who preceded him is given by Gottfried Treviranus, in his work published in 1820, Vermischte Schriften. Anatomischen und Physiologischen Inhalts,' in the chapter on the Nerves of Sense in Mammalian Animals. From this account it appears that it was Zinn who first described an optic nerve in the Mole, and declared it to be a branch of that division of the fifth pair of nerves which is distributed to the nose.

The description by Zinn was published in the fourth volume of the Commentaries of the Royal Society of Gottingen. "The optic nerve," he says, "is long and of considerable tenuity. Its origin is the same as that of the very large nerve which passes to the proboscis. It takes a long oblique course, lying above the muscles of the nose, and passing in an outward and backward direction, surrounded by dense structures, is finally