the fun feldom has admiffion. It is built of ftone, and therefore, except when the fires are kept up for the lectures, or occafional experiments, is liable to be damp. The wall, to which I allude, is immediately under a retired paffage, a very convenient place of retreat to foot-paffengers under certain circumftances of neceffity. The ground, therefore, and the adjacent wall have been for years largely impregnated with excrementitious animal fluids, in all the different stages of putrefaction. The faline efflorefcence on fuch walls is fometimes fuppofed to be alkaline, and really to be the foffile alkali; but that in this inftance, with which others of a fimilar fort probably have fome analogy, it was perfect nitre, the following remarks will evince.

The falt deflagrates readily with charcoal, or fulphur, and leaves an alkali exactly fimilar in tafte to that of the nitrum fixum. It does not deflagrate per fe-It does not give out the smell of hartfhorn, or the volatile alkali, when lixivium tartari is poured upon it either in a diffolved, or a dry ftate. A filtered folution of it fuffers no precipitation, on the addition of lixiv. tartari. A fmall quantity of this folution evaporated to cryftallization fhoots into long, filamentous, not cubical, cryftals, exactly the fame as thofe obtained from an equal quantity of folution of nitre, by the fame mode of treatment; and indeed, the efflorefcence on the walls, where

it can be feen free from duft, examined with a magnifier, appears to be formed by a congeries of fpicula of this oblong hexaëdral form, a mode of crystallization, which neither the foffile alkali, nor cubic nitre affect. These experiments fhew, that the nitre thus collected, has neither a calcareous, nor a volatile alkaline, nor a foffil alkaline, bafe, but is in every refpect perfect nitre, generated principally by the putrefaction of animal matters, certainly without the artificial addition of any prepared vegetable fubftance, (prepared at leaft by fire,) to fupply the vegetable alkali.

If you should think, Sir, upon perufal, that these obfervations will afford any amusement to the Society, you will oblige me by communicating them. If, on the other hand, you should think them too trifling, fuperficial, or tedious, I beg the favour of you to fupprefs them. And am,

With great regard,

Your fincere friend, and humble fervant,

M. WALL.

Some

Some ACCOUNT of the LIFE and WRITINGS of the late PROFESSOR GREGORY, M. D. F. R. S.By JAMES JOHNSTONE, M. D. and Soc. Reg. Medic. Edinb. Socius. Communicated by Dr. Barnes. Read December 10, 1783.

OHN GREGORY, M. D. F. R. S. Fellow

Jo

of the Royal College of Phyficians in Edinburgh, and Profeffor of Medicine in the Univerfity of Edinburgh, born at Aberdeen in 1725, was third fon of JAMES GREGORY, M. D. Profeffor of Medicine in King's College, Aberdeen; and of Anne, daughter of the Rev. George Chalmers, Principal of King's College there. The family of Dr. Gregory is of great antiquity in Scotland, and has for more than a century paft produced a fucceffion of Gentlemen, of the firft diftinction in the learned world. JAMES GREGORY, Profeffor of Mathematics, first at St. Andrews, and afterwards at Edinburgh, the Doctor's grandfather, was one of the moft eminent Mathematicians of the laft age, the age of Mathematics. He invented the Reflecting Telescope, improved by Sir Ifaac Newton. His Optica Promota, and other mathematical works, are ftill in high efteem.

David Gregory of Oxford, another of the family, the Doctor's coufin, published an excellent and complete Treatife of Aftronomy, founded upon the principles, and explanatory of the doctrine, of Sir Ifaac Newton. James Gregory, M. D. the Doctor's eldest brother, fucceeded their father as Profeffor of Medicine in King's College, Aberdeen: and the Doctor, of whom we write, has left a fon, who now holds the office of Profeffor of the Inftitutions of Medicine in the University of Edinburgh, made vacant by the election of Dr. Cullen to be fole Profeffor of Practice, after his father's death. It feems to be the destiny of this family, to enlarge scier.ce, and instruct mankind; and we hope, it will long hold this honourable distinction.

Though Dr. Gregory's father died, when his fon was very young, his education was carefully and fuccefsfully conducted by able and fkilful perfons, who were attached to his father and family, as well as to the duty they owed to their pupil. In fuch a happy fituation for improvement, Dr. Gregory made a rapid progress in his ftudies. At Aberdeen, he became thoroughly acquainted with the learned languages, and with his own; here he finished his course of philofophy, and his mathematical ftudies; for like the rest of his ancestors, he was deeply verfed in mathematical knowledge. And in this admirable fchool, where abftract fcience itself VOL. II.

G

has

has undergone a fignal reformation, and has learned to speak the language of common sense, and to adorn itfelf with the graces of taste and eloquence, Dr. Gregory cultivated an elegant and just tafte, clearness and beauty of expreffion, with precifion of judgment, and extenfive knowledge. With the circle of fcience, he poffeffed a great fhare of common fenfe, and of the knowledge of men. This he difplays in his writings; and evidently carried into his profeffion a fpirit congenial to that of the Gerard's and Beattie's, Gentlemen, with whom he lived in the clofeft habits of friendship.

Having finifhed at Aberdeen his courfe of ftudy in languages, arts, and philofophy, in 1742 he went to Edinburgh, to profecute the study of medicine.

Having attended the excellent courfes of the late Dr. Alexander Monro, the celebrated Profeffor, and Father of Anatomy there-of Dr. Alfton, on the Materia Medica, and Botany-of Dr. Plummer, on Chemistry-of Dr. Sinclair, the elegant and favourite scholar of Boerhaave, on the Inftitution of Medicine-of the fagacious Rutherford, on the Practice of Medicine-he went to Leyden in 1745, and to Paris in 1746, for farther improvement.

While at Leyden, he received a spontaneous mark of the esteem in which he was held by those among whom, and by whom, he had been edu

cated,