mensurable. For instance, the curve, Fig. 2, drawn with powers 3 and 2 respectively, give the proper form for a refracting surface of glass, whose index of refraction is 1.50, in order that rays diverging from ƒ may be refracted to F. As to the higher classes of curves with three or more focal points, we cannot at present invest them with equally clear and curious physical properties, but the method of drawing a curve by so simple a contrivance, which shall satisfy the condition m r + n r + p r" + &c. = constant, is in itself not a little interesting; and if we regard, with Mr Maxwell, the ovals above described, as the limiting case of the others by the coalescence of two or more foci, we have a farther generalization of the same kind as that so highly commended by Montucla,* by which Descartes elucidated the conic sections as particular cases of his oval curves. 2. On the Influence of Contractions of Muscles on the Circulation of the Blood. By Dr Wardrop. In this paper, Dr Wardrope states that he has endeavoured to shew, by a series of observations and experiments, that the muscles, besides being the active organs of motion, perform, by their contractions, an important office in the circulation of the arterial as well as venous blood; an office which has not hitherto been described by physiologists, but which appears to be capable of explaining several interesting phenomena in the living body, of which no satisfactory account has yet been given. 3. On the Solubility of Fluoride of Calcium in Water, and the relation of this property to the occurrence of that Substance in Minerals, and in recent and Fossil Plants and Animals. By Dr G. Wilson. After a preliminary reference to the existence of fluorine in recent and fossil bones, Dr Wilson stated that he had made a series of experiments with a view to discover what solvent carried fluoride of calcium into the tissues of plants and animals. His first trials were made with carbonic acid, which was passed in a current through water containing pure fluor-spar in fine powder suspended in it. The fluor was by this treatment dissolved, yielding a solution which precipitated oxalate of ammonia, and when evaporated left a residue Histoire des Mathematiques. First Edit. II., 102. which, on being heated with sulphuric acid, gave off hydrofluoric acid. The author was, in consequence, inclined to suppose that carbonic acid conferred upon water the power of dissolving fluoride of calcium. But on observing that long after the whole of that gas had been expelled by warming the liquid, the latter remained untroubled, he became satisfied that water alone can dissolve fluoride of calcium, contrary to the universal statement of writers on chemistry. On prosecuting the inquiry, he found that water at 212° dissolved more of the fluor than water at 60°, but he has not yet ascertained the proportion taken up by that liquid at either temperature. The aqueous solution of fluoride of calcium was found to give, with salts of baryta, a precipitate which required a large addition of hydrochloric or nitric acid to redissolve it. The author pointed out the difficulty which must in consequence occur, in distinguishing between dissolved fluoride and sulphates, and suggested that fluorides may have been mistaken for sulphates in the analysis of mineral water. He referred also to the objection which must now lie against the present method of determining the quantity of fluorine present in bodies, consisting, as it does, in converting that element into fluoride of calcium, which, in the course of the necessary analytical operations, is washed freely, and must be sensibly diminished in quantity; a fact which has of necessity been hitherto overlooked. Dr Wilson stated that he was not yet able to suggest an unexceptionable quantitative process; but that the fluoride of barium, being much less soluble than the fluoride of calcium, might, in the meanwhile, be substituted for it in the estimation of fluorine. The author proceeded to state, that in consequence of the observations he had made as to the solubility of fluoride of calcium on water, he had been led to look for that body in natural waters, and had found it in one of the wells of Edinburgh, namely, in that supplying the brewery of Mr Campbell in the Cowgate, behind Minto House. At the same time, he stated that preceding observers had already found it in other waters. He believed, however, that he was the first to detect it in sea-water, where, by using the bittern or mother-liquor of the salt-pans in which water from the Frith of Forth is evaporated, he had found it present in most notable quantity. The author referred to the presence of fluorine in sea-water, as adding another link to the chain of observed analogies between that body and chlorine, iodine, and bromine. Dr Wilson further stated, that he had confirmed the observations of Will, as to the presence of fluorine in plants, and Berzelius' discovery that fluorine exists in the secretion from the kidneys; and had, in addition, detected fluorine in the blood and milk, in neither of which has it been hitherto suspected to occur. The paper was concluded by some observations on the presence of fluorine in fossils, and its relations to animal life. The following Gentleman was elected an Ordinary Fellow - WILLIAM BALFOUR, Esq. The following Donations to the Library were announced : Proceedings of the American Philosophical Society. Vol. IV., Nos. 32 and 33. Transactions. of the American Philosophical Society held at Philadelphia, for promoting Useful Knowledge. (New Series), Vol. IX., Part 2.-By the Society. Flora Batava. Nos. 139 and 140.-By the King of the Netherlands. Journal of the Statistical Society of London. Vol. IX., Part 1. March 1846. By the Society. The American Journal of Arts and Science, conducted by Professor Silliman, B. Silliman junior, and James D. Dana, for March 1846.—By the Editors. The Quarterly Journal of the Geological Society. Vol. I., and Vol. II., Part 1.—By the Society. Proceedings of the Royal Astronomical Society. Vol. VI., Nos. 9 to 17, and Vol. VII., Nos. 1, 2, 3. Memoirs of the Royal Astronomical Society. Vol. XV. By the Society. Meteorological Observations for 1842 and 1843, made at the Bombay Government Observatory. By George Buist, LL.D., in the charge of the Observatory. Magnetic Observations made at the Bombay Government Observatory from May 1842 to Dec. 1843. By George Buist, LL.D. Tracings of the Wind-Gauge for 1842 and 1843, made at the Bombay Government Observatory from May 1842 to Dec. 1843. By George Buist, LL.D.-By George Buist, LL.D. Journal of the Asiatic Society of Bengal. No. 162.-By the Society. Memoirs and Proceedings of the Chemical Society. Part 16.-By the Society. Maps of the Geological Survey of the United Kingdom of Great Britain.-By Sir H. T. De la Beche, Director-General of the Geological Survey. Monday 20th April 1846. The RIGHT REV. BISHOP TERROT, Vice-President, in the Chair. The following communications were read : 1. On the Constitution and Properties of Picoline, a new organic base from Coal-Tar. By Dr T. Anderson. The author, after alluding to the investigations of the oily bases in coal tar, by Hoffmann, who had failed in obtaining Runge's pyrrol, stated, that in searching for that substance among the more volatile products of the distillation of coal-tar, he had been enabled to confirm its existence in small quantity, as well as that of the new base to which he has given the name of picoline. Picoline is obtained in the pure state by several successive distillations of the mixed bases contained in coal-tar, after the perfect separation of pyrrol and empyreumatic oils, by processes described at length in the paper, and finally by collecting the product which distilled at 272° Fahrenheit. The analysis of the base purified by these processes, gave the following mean result, viz. :— This corresponds with the formula C12 H, N, which is that of aniline; and the author further found by the analysis of the platinum salt of picoline, that its atomic weight is identical with that of aniline. The identity in constitution, however, of these substances is accompanied by an entire difference in properties. Picoline having a specific gravity of 0.955 boiling at 272°, and being soluble in water in all proportions; it is incapable of giving the violet colour with chloride of lime, and the yellow colour to fir wood moistened with hydrochloric acid, which are produced by aniline, and it gives, with chloride of gold, a highly characteristic precipitate, soluble in hot water, and deposited, on cooling, in delicate yellow needles. The author observed that these properties approximated in some respects to those of Unverdorben's odorin, and stated that he had separated from the oleum cornu cervi, a mixture of several oily bases, one of which was soluble in water, but which did not agree perfectly either with the characters of picoline, or those which Unverdorben has attributed to odorin. The author then details the properties and constitution of the compounds of picoline, which differ in many respects from those of aniline. It gives with sulphuric acid an acid compound which deliquesces rapidly in the air, and which has the formula C12 H7 N + 2 (H O, S O 3). Its platinum salt is identical in constitution with that of aniline, but its mercury compound is C12 H7 N + Hg Cl2, while that of aniline is 2 (C12 H7 N) + 3 Hg Cl 2. The author then treats of the products of the decomposition of picoline, a branch of the subject on which, owing to the small quantity of the substance at his disposal, he was enabled only to make a few observations, which, however, tend to shew that the action of reagents on it is remarkably different from that which they produce on aniline. The action of nitric acid was found to be extremely slow and partial, long continued ebullition producing only a very slight evolution of nitrous acid, without any of the blue colour which aniline gives, and apparently without the formation of carbazotic acid. Bromine gives an oily product heavier than water, and different, of course, from the solid bromaniloid of Fritsche. The author concludes by remarking, that the present is the first perfectly established case of isomerism among organic bases, those previously recorded being devoid of absolutely conclusive evidence, and by pointing out the interest which attaches to the isomerism of two substances such as aniline and picoline, which are members of one of the most interesting and extensive groups of organic substances, the indigo, salicyl, and benzoil series. 2. Notice of Polished and Striated Rocks recently discovered on Arthur Seat, and in some other places near Edinburgh. By David Milne, Esq. Mr Milne stated, that, in the gully situated between Arthur Seat and Sampson's Ribs, a great extent of rock had been recently exposed (by the removal of clay and other superficial deposits) which was found to be smoothed as well as furrowed or scratched. The gully is about 30 feet wide, at the lowest level to which it |