Fig. 1, represents the rain gauge in perspective. G the body of the gauge, F its funnel, L the lid or cover, v the valve, hinged to the lower orifice of the funnel, s the spring to close the valve, w a wire to conduct the drainings of the funnel into the body of the gauge. ARTICLE VIII. On Baryto-Calcite. By H. J. Brooke, FRS. &c. (To the Editors of the Annals of Philosophy.) GENTLEMEN, July 15, 1824. MR. BROUGHTON, before he left London, favoured me with specimens of a mineral from Cumberland which had been considered to be carbonate of barytes, but it was very evident that the crystals did not resemble the ordinary figures of carbonate of barytes, and the substance was, therefore, regarded by Mr. Broughton as something new. P The external surface of the specimens is coated with sulphate of barytes; but the internal mass frequently contains cavities which are lined, and nearly filled with crystals. The primary form of these is an oblique rhombic prism, as shown in the annexed figure, the cleavage being parallel to the planes P, M, and M. M h M on M' M on h. All the crystals I have seen are modified on some of the edges and angles, and are lengthened in the direction of the edges of the modifying planes, presenting the character of prisms terminated by the bright planes P, a, M, and h, of the figure. The modifying planes are, however, so numerous, irregular and dull in my specimens, that I have not obtained sufficiently good or corresponding measurements to enable me to ascertain their character, and they are, therefore, omitted in the drawing. The mineral is translucent with a slight tinge of a yellowishbrown colour. Its lustre rather more waxy than carbonate of barytes. Its hardness is between that of carbonate and fluate of lime. Its specific gravity, as ascertained by Mr. Children, is 3.66. The name baryto-calcite has been given from its chemical composition, as ascertained by Mr. Children. * The mean specific gravity of carbonate of barytes carbonate of lime is 3.5.-C Chemical Examination of the Baryto-Calcite. By J. G. Children, FRS, &c. With the blowpipe this mineral exhibits the following cha racters. In the forceps, in the oxidating flame, it neither fuses nor decrepitates; its surface becomes green, and the point of the flame, beyond the assay, assumes a light greenish-yellow colour. In the reducing flame the superficial green colour disappears. The assay, after being ignited, browns moistened turmeric paper. Heated to redness, in a glass tube, it merely gives off a little moisture. By heat the assay becomes strongly phosphorescent, shining with a pale-yellow light, very similar to that of the common glow-worm. With soda, on the platina wire, in the oxidating flame, it gives a bluish-green opaque mass. In the reducing flame the green colour is discharged. With borax, in the oxidating flame, dissolves readily into a perfectly diaphanous globule of a beautiful light amethystine colour. The globule retains its transparency in the reducing flame, but entirely loses its colour. With salt of phosphorus, dissolves very readily; the globule is perfectly transparent, and in the oxidating flame yellow while hot; when cold, colourless. In the reducing flame the globule is colourless, and, while hot, transparent; when cold, its transparency is slightly disturbed. Analysis. To ascertain the proportions of its elements, I dissolved the mineral in muriatic acid, diluted the solution very largely with distilled water, and precipitated the barytes by sulphate of ammonia; boiled the precipitate to take up any sulphate of lime that might have been thrown down, filtered, and washed the precipitate, till the washings ceased to give any cloud with oxalate of ammonia, adding the washings to the solution from which the sulphate of barytes had been separated. The solution, being first reduced by evaporation, was then boiled with a solution of carbonate of potash, which threw down the lime in the state in which it originally existed in the mineral. Treated in this manner, 20 grs. gave Grains. Sulphate of barytes 15.55 grs.#carbonate of barytes 13-18 Carbonate of lime. 6.72 19.90 A minute portion, not exceeding one or two-tenths of a grain, remained undissolved, and consisted chiefly of sulphate of barytes. Traces of iron and manganese were also obtained, as previously indicated by the blowpipe, but I could not detect any appearance of magnesia. The mineral effervesces of course very strongly with acids, and, when finely pulverised, its powder has a very light flesh-coloured or rosy tint. According to Brande's Table of Prime Equivalents, the weight of the atom of carbonate of barytes is to that of carbonate of lime as 100: 50, or as 2: 1. The theoretical composition of this mineral, therefore, (disregarding the insoluble sulphate, and the metallic oxides, as not essential to it) accords very nearly with that obtained by experiment, as appears below : Hence we may consider it as containing an atom of each element. ARTICLE IX. On the Transmission of Electricity through Tubes of Water, &c. By Mr. Lewthwaite. (To the Editors of the Annals of Philosophy.) GENTLEMEN, Rotherhithe, July 9, 1824. ALLOW me to intrude myself on your pages to correct an error committed by Mr. Woodward in the last number of the Annals. Mr. W. says, the effects of electricity on loose gunpowder when transmitted through tubes of water, were communicated by me to Mr. L. some time previous to the publication of his letter. The natural inference to be drawn from this sentence is, that I am indebted to him for the experiment in question. This, I can assure Mr. W. is not the case; it was originally communicated to me by Mr. Tuther about fourteen years ago. The experiment relative to the conducting power of ether, alcohol, and acids, published in the Institution Journal, originated while I was experimenting with the water tube, nor had I the least idea that Mr. W. was investigating the conducting power of those fluids until some time after the publication of my letter. I am, Gentlemen, your humble servant, JOHN LEWTHWAITE. P. S. An account of the experiment of firing loose gunpowder by the water tube may be found in Imison's Elements of Science and Arts, vol. i. p. 469. ARTICLE X. On the Nature of the Acid and Saline Matters usually existing in the Stomachs of Animals. By William Prout, MD. FRS.* THAT a free, or at least an unsaturated acid usually exists in the stomachs of animals, and is in some manner connected with the important process of digestion, seems to have been the general opinion of physiologists till the time of Spallanzani. This illustrious philosopher concluded, from his numerous experiments, that the gastric fluids, when in a perfectly natural state, are neither acid nor alkaline. Even Spallanzani, however, admitted that the contents of the stomach are very generally acid; and this accords not only with my own observation, but with that, I believe, of almost every individual who has made any experiments on the subject. With respect to the nature of this acid, very various opinions have been entertained. Some of the older chemists seem to have considered it as an acid, sui generis; by others it was supposed to be the phosphoric, the acetic, the lactic acid,† &c. No less various have been the opinions respecting its origin and use; some supposing that it is derived from the stomach itself, and is essential to the digestive process; others, that it is derived from the food, or is a result of fermentation, &c.; in short, there seems to be no physiological subject so imperfectly understood, or concerning which there has been such a variety of opinions. The object of the present communication is to show, that the acid in question is the muriatic acid, and that the salts usually met with in the stomach are the alkaline muriates. As to the origin and use of these principles, as well as the occasional appearance of other acids, &c. in the stomach, I reserve what I have to say on these subjects till a future opportunity, and shall merely remark at present, that the facts now adduced seem to be intimately connected, not only with the physiology and pathology of the digestive process, but with other important animal functions. Having ascertained the circumstances above-mentioned in a general manner, and by means which it would be here unnecessary to detail, an attempt was made to contrive some unexcep * From the Philosophical Transactions for 1824, Part I. + After I had discovered the principal fact related in this paper, I was surprised to find how nearly Scopoli had come to the same conclusion. He did not indeed come to the conclusion, as far as I can ascertain, that free muriatic acid exists in the stomach, but he advanced the opinion, that the muriatic acid, in union with ammonia, found in such abundance in the stomach of ruminating animals, is secreted by that organ itself. The only account of Scopoli's experiments I have seen is in Johnson's Animal Chemistry, i. 183. tionable method by which their truth might not only be satisfactorily demonstrated, but at the same time that the relative quantities of the different principles might be determined: after various attempts, the following processes were adopted for these purposes. The contents of the stomach of a rabbit, fed on its natural food, were removed immediately after death, and repeatedly digested in cold distilled water till they ceased to impart any thing to that fluid. The whole of these different portions of fluid, which always exhibited strong and decided marks of acidity, were then intimately mixed together, and after being allowed to settle, were divided into four equal portions. 1. The first of these portions was evaporated to dryness in its natural state, and the residuum burnt in a platinum vessel; the saline matter left was then dissolved in distilled water, and the quantity of muriatic acid present determined by nitrate of silver in the usual manner; the proportion of muriatic acid in union with a fixed alkali, was thus determined. 2. Another portion of the original fluid was supersaturated with potash, then evaporated to dryness, and burnt, and the muriatic acid contained in the saline residuum determined as before. In this manner the total quantity of muriatic acid present in the fluid was ascertained. 3. A third portion was exactly neutralised with a solution of potash of known strength, and the quantity required for that purpose accurately noticed. This gave the proportion of free acid present; and by adding this to the quantity in union with a fixed alkali, as determined above, and subtracting the sum from the total quantity of muriatic acid present, the proportion of acid in union with ammonia was estimated. But as a check to this result, the third neutralised portion abovementioned was evaporated to dryness, and the muriate of ammonia expelled by heat, and collected. The quantity of muriatic acid this contained was then determined as before, and was always found to represent nearly the quantity of muriate of ammonia as before estimated; thus proving the general accuracy of the whole experiments beyond a doubt. 4. The remaining fourth portion of the original fluid was reserved for miscellaneous experiments, and particularly for the purpose of ascertaining whether it contained any other acid besides the muriatic. The experiments abovementioned seemed to preclude the possibility of the presence of any destructible acid; and the only known fixed acids likely to be present were the sulphuric and phosphoric; the muriate of barytes, however, neither alone, nor with the addition of ammonia, produced any immediate precipitate,* showing the *It may be proper to remark, that ammonia, after some time, caused a flocculent precipitate, consisting of the earthy phosphates in union with vegetable and animal matter, and that after combustion, traces of sulphuric acid, the result of that process, were very perceptible. But it is evident, from the experiment related in the text, that neither of these acids previously existed in the original fluid in a free state. |