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Wollaston's estimate the dry acid in liquid acid of sp. gr. 1.5 is to that of Dr. Ure, as 74.895 to 79.71.

Before I mention the experiments which I have made on this subject, I shall notice and compare Dr. Ure's statements with each other. I have already quoted a passage, in which he represents acid of a certain density, as consisting of 7 atoms, water 79.24 united to one atom of dry acid 67.5; these numbers appear to be from Dr. Wollaston's scale, and of course they are considered as correctly representing the quantity of water and acid in question. If, however, we compare these numbers with those which are to be derived from Dr. Ure's analysis of liquid nitric acid of 1.5, it will appear that this acid is composed of 67.5, one atom acid united to 16.79 water, and consequently of one atom acid, and one atom and 44% of an atom of water, a conclusion, of which it may be truly stated in the language of Dr. Ure, that it "exhibits internal proofs of inconsistency and error." To examine the subject experimentally as well as theoretically, I prepared some pure nitric acid, which had a sp. gr. of 1.496, so nearly 1.5, that they may be considered as identical in experiment. Of this acid, I saturated 150 grains with potash, and evaporated the solution of nitrate of potash to dryness; the salt obtained weighed 215 grs.; and according to Dr. Ure, 61 of nitre contain 32.394 of dry acid, agreeing very nearly with 32.5, which is Dr. Wollaston's proportion, as then 61 give 32.5, 215 must contain 114.55 of dry acid derived from 150 of liquid. One hundred parts of the liquid acid appear to be composed of

76.367 acid

23.633 water

700.000.

The dry acid it will be seen exceeds Dr. Wollaston's estimate by 1,472, and is less than Dr. Ure's by 3.343.

It is easier, for obvious reasons, to obtain more accurate reaults with carbonate of lime than with carbonate of potash; I shall therefore now state the experiments which I have made with this substance. I ascertained some years since, that 476 grains of carbonate of lime require 681.75 of liquid nitric acid,

sp. gr. 1.5, for their decomposition, and this determination has been noticed by Dr. Wollaston, as agreeing very closely with his views of the composition of liquid nitric acid. In order to try how much nitrate of lime would be obtained from the decomposition of a given weight of the carbonate, I put 150 grains of double refracting spar into a quantity of nitric acid insufficient to decompose the whole of it; the platina crucible containing the solution of nitrate of lime, and the undecomposed carbonate, was heated till all the water was dissipated; on weighing, I obtained 243.2 grains. After dissolving the nitrate of lime in water, I found 3.4 of carbonate unacted upon; if then we subtract 3.4 from 150, the quantity of carbonate of lime originally used, and also from 243.2 the weight of the nitrate and carbonate of lime, it will appear that 146.6 of carbonate, were converted into 239.8 of nitrate of lime.

The experiments which I have now mentioned, show that 63 of carbonate of lime are decomposable by 90.23 of nitric acid 1.5, and that 103.05 of nitrate of lime result from their action, it will be seen by the scale, that 63 of carbonate of lime contain 35.46 of lime, which deducted from 103.05 the nitrate of lime give 67.59, as the dry nitric acid contained in 90.23 of liquid acid of 1,5, or it consists of 74.91 acid + 25.09 water, a determination in which it will be seen, that the acid differs only about a part from the quantity stated by Dr. Wollaston.

With respect then to the composition of liquid, as well as of dry nitric acid, I conclude in direct opposition to Dr. Ure, that the subject is neither obscure nor mysterious; on the contrary, it appears to me, that the eminent philosophers, whose results he quotes to condemn, or whose conclusions he confirms or copies, have effected all the certainty which can be derived, from the "best directed efforts of modern science."

ART. XIX. Proceedings of the Royal Society of London.

Thursday, Jan. 8th, and 15th. THESE meetings of the Society were occupied by the reading of a paper presented by Dr. Brewster, relating to the laws of double refraction in regularly crystallized bodies.

Jan. 22. A paper was communicated by Sir Everard Home, containing additional facts respecting certain fossil remains, formerly described by the author in the Philosophical Transactions. The analogy between the animal alluded to and cartilaginous fishes, is destroyed by the examination of the bones of the ster num, which much resemble those of the Ornithorynchus Paradoxus. Sir Everard proved that the fossil animal lived in water by the form of its vertebræ ; while from the shape of its chest it was shewn to have breathed air. In concluding his observations upon these subjects, Sir Everard remarked upon the interest of discovering in this country fossil bones which bear an analogy to those of an animal of New Holland of so peculiar a character as the Ornithorynchus

Jan. 29. An extremely curious and important paper was read to the Society by Captain Kater, giving an account of his expe riments for determining the length of the pendulum vibrating seconds in the latitude of London. We have already hinted that the President and Council adjudged the Copley Medal to Captain Kater for this important inquiry; after shewing the objections to all methods hitherto practised for accurately ascertaining the length of the seconds pendulum, Captain Kater detailed with great perspicuity the mode of proceeding which he had successfully adopted, and which was founded on the reci procity of the centres of suspension and oscillation. Captain Kater then describes the various corrections for temperature, pressure, and height above the sea, and having shewn the advantages of his different methods, concludes, that the length of the pendulum vibrating seconds in vacuo at the level of the sea, measured at the temperature of 62° Fahr. and the latitude of

the place of observation deduced from the data contained in the Trigonometrical Survey, being 51° 31' 8"4 North, is,

By Sir George Shuckburgh's Standard,
By General Roy's Scale,

By Bird's Parliamentary Standard,

39,13860 inches.

39.13717 do.

39,13843. do.

Feb. 5th. Captain Kater communicated a paper on the length of the French metre, estimated in parts of the English standard. -For the purpose of ascertaining this important point, two metres were sent from Paris-the one is a bar of platinum of the exact length, and called the metrè à bouts-the other is a somewhat longer bar of the same metal upon which the length of the metre is shewn by two very fine lines-it is called a metre à traits. The mean result of several very delicate experiments gave the length of the French metre 39,37071 inches of Sir George Shuckburgh's scale-or 39,37052 inches of Bird's Parliamentary standard.

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At the same meeting a paper was read by Thomas Andrew Knight, Esq. on the office of the heart-wood of trees. Mr. Knight's object in this paper was to shew that the heart-wood of trees is a winter reservoir for the organizable matter required for their germination in the spring, and that the presence or absence of this reservoir is connected with the annual, biennial, and perennial duration of plants. The annual having no such reservoir, is entirely exhausted in forming its flowers and seeds. A biennial fills its reservoir one season, and exhausts it the next, and in the tree, part of the sap descends to form roots, and part ascends to produce buds, and it also forms a new annual layer of bark. Mr. Knight's paper also contained some statical experiments on the quantity of water contained in the alburnum of different trees, at different seasons of the year.

Feb. 12. A paper by Dr. Marshall Hall was read on the combined agencies of oxygen and water in producing the oxidizement of iron. Dr. Hali has shewn in this paper, that iron is incapable of decomposing water at common temperatures, and that it becomes rusty or oxidized when exposed to common water, as is generally stated; but from the decomposition of the

air in water-he also shews that nitrogen alone is evolved and no hydrogen; and that when water is deprived of atmospheric air, or oxygen, iron retains a clear and bright surface though exposed for many months to its action.

At the same meeting Sir H. Davy read some remarks on the fallacy of the experiments, in which water is said to have been formed by the decomposition of chlorine.

These experiments go to prove that the oxygen required to form the water obtained in the experiment alluded to, is derived, not as has erroneously been asserted, from the chlorine, but from other sources, which had eluded the vigilance of the experimentalists.

Feb. 19th. A letter from George Rennie, Esq. to Dr. Young, was read, containing an account of some experiments on the strength of materials. Mr. Rennie shews in this communication, that the strength of cast iron is extremely various according to the circumstances under which it has been cast. Thus, vertical castings are stronger than horizontal, &c. Observations are annexed on the relative strength of woods, stones, and other building materials.

Feb. 26th. A paper was presented by Thomas Knight, Esq. containing a solution of an analytical problem; and another by J. F. W. Herschell, Esq., "on circulating functions, and on the integrations of a class of equations of finite differences into which they enter as coefficients."

Mar. 5. A paper was read to the Society on the Parallax of certain fixed stars, by the Rev. John Brinkley, D. D. F. R. S.; and at the same meeting, Sir Everard Home communicated some additions to his Croonian Lecture. (See page 362, Vol. 4, of this Journal.) Captain Kater having put the author in possession of more accurate measurements of the globules of the blood than those formerly given, Sir Everard now stated these to the Society and is induced to consider the diameter of a globule of the blood as = g of an inch instead of 2005.

This paper also contains many additional experiments and observations relative to the formation of tubuli by the extrication of air during the coagulation of blood.-The author also

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