A Method of Fixing Particles on the Sappare Thomson's Annals of Philosophy, Vol. XXII; New Series, Page 90 Vol. VI, 1823, p. 412. On some Compounds of Fluorine 94 Thomson's Annals of Philosophy, Vol. XXIII; New XXIII; An Examination of some Egyptian Colors 101 Thomson's Annals of Philosophy, Vol. XXIII; New Some Observations on Mr. Penn's Theory concerning the formation of the Kirkdale Cave 103 Thomson's Annals of Philosophy, Vol. XXIV; New Series, A letter from Dr. Black describing a very sensible Balance. A Method of Fixing Crayon Colors Thomson's Annals of Philosophy, Vol. XXVI; New Series, II.-REVIEWS. 117 120 A Memoir on the Scientific Character and Researches of SON On the Works and Character of James Smithson, by J. R. MCD. IRBY INDEX 123 AN ACCOUNT OF SOME CHEMICAL EXPERI MENTS ON TABASHEER. From the Philosophical Transactions of the Royal Society of London. Vol. LXXXI, for the year 1791, Part 2, p. 368.-Read July 7, 1791. The Tabasheer employed in these experiments was that which Dr. RUSSELL laid before the Society, as specimens of this substance, the evening his Paper upon the subject was read.* There were seven parcels. No. 1 consisted of Tabasheer extracted from the bamboo by Dr. RUSSELL himself. No. 2 had been partly taken from the reed in Dr. RusSEL's presence, and partly brought to him at different times by a person who worked in bamboos. No. 3 was the Tabasheer from Hydrabad; the finest kind of this substance to be bought. Nos. 4, 5, and 6 all came from Masulapatam, where they are sold at a very low price. These three kinds have been thought to be artificial compositions in imitation of the true Tabasheer, and to be made of calcined bones. No. 7 had no account affixed to it. The Tabasheer from Hydrabad being in the greatest quantity, and appearing the most homogeneous and pure, the experiments were begun, and principally made, with it. Hydrabad Tabasheer. (No. 3.) § I. (A) This, in its general appearance, very much resembled fragments of that variety of calcedony which is known to mineralogists by the name of Cacholong. Some pieces were quite opaque, and absolutely white; but others *See Phil. Trans. Vol. LXXX, p. 283. possessed a small degree of transparency, and had a bluish cast. The latter, held before a lighted candle, appeared very pellucid, and of a flame colour. The pieces were of various sizes; the largest of them did not exceed two or three-tenths of an inch cubic. Their shape was quite irregular; some of them bore impressions of the inner part of the bamboo against which they were formed. (B) This Tabasheer could not be broken by pressure between the fingers; but by the teeth it was easily reduced to powder. On first chewing it felt gritty, but soon ground to impalpable particles. (C) Applied to the tongue, it adhered to it by capillary attraction. (D) It had a disagreeable earthy taste, something like that of magnesia. (E) No light was produced either by cutting it with a knife, or by rubbing two pieces of it together, in the dark; but a bit of this substance, being laid on a hot iron, soon appeared surrounded with a feeble luminous auréole. By being made red hot, it was deprived of this property of shining when gently heated; but recovered it again, on being kept for two months. (F) Examined with the microscope, it did not appear dif ferent from what it does to the naked eye. (G) A quantity of this Tabasheer which weighed 75.7 gr. in air, weighed only 41.1 gr. in distilled water whose temperature was 52.5 F. which makes its specific gravity to be very nearly 2.188. = Mr. CAVENDISH, having tried this same parcel when become again quite dry, found its specific gravity to be = 2.169. Treated with water. § II. (A) This Tabasheer, put into water, emitted a number of bubbles of air; the white opaque bits became transparent in a small degree only, but the bluish ones nearly as much so as glass. In this state the different colour pro duced by reflected and by transmitted light was very sensible. (B) Four bits of this substance, weighing together, while dry and opaque, 4.1 gr., were put into distilled water, and let become transparent; being then taken out, and the unabsorbed water hastily wiped from their surface, they were again weighed, and were found to equal 8.2 gr. In the experiment § I. (G), 75.7 gr. of this substance absorbed 69.5 gr. of distilled water. (C) Four bits of Tabasheer, weighing together 3.2 gr. were boiled for 30' in half an ounce of distilled water in a Florence flask, which had been previously rinced with some of the same fluid. This water, when become cold, did not shew any change on the admixture of vitriolic acid, of acid of sugar, nor of solutions of nitre of silver, or of crystals of soda; yet, on its evaporation, it left a white film on the glass, which could not be got off by washing in cold water, nor by hot marine acid; but which was discharged by warm caustic vegetable alkali, and by long ebullition in water. Upon these bits of Tabasheer, another half ounce of distilled water was poured, and again boiled for about half an hour. This water also on evaporation left a white film on the glass vessel similar to the above. The pieces of Tabasheer having been dried, by exposure to the air for some days in a warm room, were found to have lost one-tenth of a grain of their weight. To ascertain whether the whole of a piece of Tabasheer could be dissolved by boiling in water, a little bit of this substance, weighing three-tenths of a grain, was boiled in 36 ounces of soft water for near five hours consecutively; but being afterwards dried and weighed, it was not diminished in quantity, nor was it deprived of its taste. With vegetable colours. § III. Some Tabasheer, reduced to fine powder, was boiled for a considerable time in infusions of turnsole, of logwood, |