Imatges de pÓgina
[ocr errors]

hence to infer, that all these medicines, when taken into the stomach, are inert till they are received into the blood, and distributed to the parts upon which they produce sensible effects?

A paper on the composition and combinations of phosphoric acid, by Thomas Thomson, M. D. was commenced, and concluded at a succeeding meeting. According to Lavoisier's original researches, one part by weight of phosphorus unites to one and a half of oxygen to constitute phosphoric acid, a result which has been verified by several succeeding chemists, and more especially by Sir Humphry Davy, who regards this acid as composed of 20 phosphorus +30 oxygen. But, according to the present analyst, 100 phosphorus unites only to 123.46 oxygen to produce phosphoric acid. Rose found the quantity of oxygen yet smaller. Dr. Thomson verifies his conclusion by reference to the analysis of phosphate of lead, and by taking a mean of methods, ultimately considers phosphoric acid as consisting of 100 phosphoric + 123,37 oxygen. He then proceeds to examine the compounds which the phosphoric acid produces by combining with lime, the phosphates of lime, of which, he' conceives, there exist no less than six varieties, each of definite constitution: they bear the following names, 1. Quadrosteo-phosphate; 2. Binosteo-phosphate; 3. Bige-phosphate; 4. Osteo-phosphate; 6. Ge-phosphate. The constituents of many other phosphates are detailed in this communication; but as it would be indecorous to criticise a paper not published, and as without criticism the details would be of little avail, it is unnecessary at present to pursue them. Dr. Thomson infers from his numerous experiments, that the atomic doctrines of Berzelius are not worthy the confidence which he once put in them.

Proceedings of the Royal Society of Edinburgh.

[From the Journal of Science and the Arts, No. II, for 1816.]

APRIL 1. Dr. Murray communicated some additional Remarks on the Construction and Use of a Lamp for illuminating Coal Mines. The lamp was exhibited: it is well calculated for giving a strong steady light, and from being supplied with air from a tube reaching to the floor, affords great security.

April 15. Dr. Murray communicated the first part of a Paper on the Analysis of Sea Water. The methods employed were suggested by the views formerly delivered in Dr. Murray's paper on the analysis of the mineral waters of Dumblane, and the conclusions were conformable to these views.

April 29. Mr. Hugh Murray read an essay "On the Ancient Geography of Central and Eastern Asia, with Illustrations, derived from recent Discoveries in the North of India." Mr. M. conceived that the ancients, particularly Ptolemy and Pliny, knew more respecting this quarter of the world than is generally supposed. The modern discovery respecting the course of the rivers of the Punjab, and their union into one, before falling into the Indus, is a mere restoration of Ptolemy's map of these rivers. The western tributaries, so erroneously delineated by the moderns till the Cabul mission, are represented by him with nearly equal precision. Mr. M. conceives that Ptolemy's statements, carefully analysed, form a pretty correct outline of central and eastern Asia. Thus the extensive tract of the Sacarum Regio, bounded on the south by India, from which it is separated by the Imaus (Hemalleh), corresponds in all its features with Little Thibet. Scythia extra Imaum, bounded by India beyond the Ganges, from which it is separated by the Mons Emodus, will then be Great Thibet, extended indefinitely into Tartary. Serica, then, bounded on the south partly by India beyond the Ganges, and partly by Siam (Sinarum Regio), will, under some modifications, be China. The very character of the Seres, mild, timid,

unwarlike, jealous of foreigners, and carrying on trade only at fixed frontier stations, represents exactly and exclusively the modern Chinese. Mr. M. then endeavours to show, that the prevailing systems of d'Anville, Gosselin, &c. are founded on an undue contempt of ancient authorities, and upon some slight resemblances of name, which, compared with the grand and permanent features of nature, cannot be allowed much weight in such an investigation.

At the same meeting Dr. Brewster laid before the Society a Paper on a new optical and mineralogical Property of calcareous Spar. Having formerly shown (Phil. Trans. 1815, p. 270) that the colours exhibited by some specimens of calcareous spar were produced by a thin film or interrupting stratum which divided the polarised light into its complementary tints; Dr. Brewster examined several new specimens which possessed this property, in order to ascertain the axes of this film. In the course of this examination he discovered that a prism could be cut out of a rhomboid of this kind, which, when combined with another prism of common calcareous spar, exercised such an action upon the transmitted light, that the combined prisms possessed none of the properties described by Huygens and Newton, that is, none of the four images vanished in any position of the second prism, but continued visible during the whole of its revolution. The combined prisms however recovered their usual property when the opposite face of the first prism received the incident pencil. Hence it follows, that the pencils were depolarised by the interrupting film; and Dr. B. has shown that the film has all its axes constantly inclined 45° to those of the mass which contains it. As the particles of the film are not symmetrically combined with those of the mass, they are not joined by their poles, and consequently they do not come into optical contact, light being always reflected at the junction. Some specimens possess two and even three sets of films or veins, each set being parallel to the common sections of the three surfaces which contain the solid angle.

May 6. Dr. Brewster read a Paper "on the Communication of double Refraction to Glass, and other hard and soft sub

stances that refract singly, by mechanical Compression and Dilatation." Having inferred from the optical properties of heated glass, that its doubly refracting structure was owing to a variation of density, Dr. B. endeavoured, by means of screws, to produce the same mechanical change upon glass, and he found that in every case the glass was converted into a doubly refracting crystal while the pressure was continued. He next took long plates of glass with polished edges, and found that by slightly bending them with the hand, the convex or dilated side had the same structure as one class of doubly refracting crystals, while the concave or compressed side had the same structure as the other class. Muriate of soda, fluor spar, diamond, obsidian, semi-opal, horn, tortoise shell, amber, gum copal, caoutchouc, rosin, phosphorus, the crystalline lens, and the sclerotic coat of fishes, and other substances that have not the property of double refraction, receive it by compression or dilatation; while no effect whatever is produced upon doubly refracting crystals by the most powerful pressure. Many curious results were obtained by inclosing the glass in fluid metal and observing the changes which it underwent from the contraction of the metal in cooling. Upon the preceding principles is founded a chromatic dynamometer for measuring the intensity of forces, and various instruments for indicating differences of humidity and temperature by the expansions or contractions which they produce.

The second part of this paper related to the communication of double refraction either transiently or permanently to animal jellies, by gradual induration, or by mechanical compression or expansion.

It follows from these principles that in all crystals of one class there is a difference of density related to the axis; that in those of the other class, the difference of density is related to a line at right angles to the axis; and that in those crystals which have the structure of both classes the difference of density is related to two rectangular axes.

May 20. The conclusion of Dr. Murray's Paper on the Analysis of Sea Water was read. He gave also the result of an analysis of a salt which is formed in the large way from the

brine of sea water, which seems hitherto to have escaped observation. It is a sulphate of magnesia and soda which crystallizes in very regular rhombs, occasionally truncated on some of the edges and angles. It contains a much smaller quantity of water of crystallization than either sulphate of soda or sulphate of magnesia; is less disagreeable to the taste, and differs from both in all its other properties. It has not hitherto been applied to any useful purpose, but it may probably form a very excellent purgative salt.

A Barometer was exhibited to the Society with a communication from Mr. Kennedy, suggesting a mode of rendering this valuable instrument more portable, and less liable to damage by the concussion of the mercury against the upper part of the tube: this it is proposed to prevent by introducing a small bell-shaped bulb of glass, attached to a spiral spring and fastened to the top of the tube. This improvement appears to be calculated to prevent the accidents which so frequently occur in the use of this instrument.

Dr. Gordon communicated certain observations to the Society, tending to establish the pathological fact, that the appearance called the buffy coat, or inflammatory crust, is not confined to venous blood, but is also occasionally seen on arterial blood, in similar states of the system. Dr. G. had himself an opportunity of seeing this appearance on arterial blood in one instance; and three other instances, in which it had occurred, were mentioned to him by Dr. Gregory, Mr. Ashburner, and Mr. Wishart.

Dr. Gordon also stated to the Society, that by a series of observations on the muscles of the living human body, during surgical operations, on the muscles of limbs immediately after amputation, and on the muscles of several of the lower animals, in a variety of circumstances, he conceived he had established, that the muscular fibre, during its contraction, does not exhibit the slightest appearance of rugæ, but remains perfectly straight; and that it does not undergo any perceptible enlargement in its transverse diameter.

May 27. Mr. Mackenzie read a Criticism on the Tragedy of Bertram lately published by Mr. Maturin.

« AnteriorContinua »