is a simple mixture or a chemical compound of oxygene and chlorine, but it affords a strong additional confirmation that the character of acidity does not depend upon any single elementary principle, since this substance which contains four proportions of oxygene, exhibits no acid properties whatever.

Farther analytical Experiments relative to the Constitution of the Prussic, of the ferruretted chyazic, and of the sulphuretted chyazic Acids, and to that of their Salts, together with the Application of the atomic Theory to the Analysis of these Bodies. By Robert Porrett, Jun. Esq.

This, like Mr. Porrett's former paper on the Prussic acid and its combinations, is an able and ingenious communication, but not very susceptible of abridgement, owing to the nature of its details, and the tabular form into which many of the results both of experiment and calculation are thrown. As the great volatility of the Prussic acid, appeared to Mr. P. to present considerable difficulties to any attempt to an lyse it in its uncombined state, he resolved to take advantage of its combination with mercury, and to make the Prussiate of that metal the basis of his investigations. For the purpose of analysing this salt Mr. P. adoptet expedients suggested by his former discoveries. The Prussia of mercury dissolved in hot water, was decomposed by the hydreguretted sulphuret of soda, which was added until no farther precipitation was occasioned The mercury was thus obtained in the state of black sulphuret, and the Prussic acid which was converted at the moment of decomposition into sulphuretted chyazic acid, was afterwards precipitated from the solution by adding a solution of the sulphates of copper and black oxide of iron to the liquid in which it was contained. By this means the acid was precipitated in combination with protoxide of copper in the form of a white insoluble salt. By an accurate examination of the results, and comparing them with those of former experiments, Mr P determined the composition of Prussiate of mercury to be 13.8. of acid, and 86.2. of red oxide of mercury. The proportions of the constituents of the Prussiate of mercury being thus determined, Mr. P. next decomposed the Prussic acid in this salt. by heating it in contact with an additional quantity of the red oxide of mercury; the proportions employed for the combustion of the acid being multiples of that which the salt contains, and which were added in succession until the whole of the acid was found to be decomposed. This effect was not produced until the quantity of red oxide of mercury added, was five times that contained in the salt; with this proportion the quantity of azote, and carbonic acid, were at their maximum, but with smaller proportions there was always a quantity of undecomposed Prussic acid in the

gaseous products. In all cases Mr. P. observed, that the volume of azote was exactly equal to that of the Prussic acid, and the volume of carbonic acid was invariably twice that of the azotic gas, and was sufficient to account for only one third of the oxygen which was consumed. From these data Mr. P. was enabled to construct a table, and thus to correct the inaccuracies unavoidable in delicate experiments on small quantities of matter. By these means he determined the composition of Prussic acid to be in 100 parts, Carbon 34.8. Azote 40.7. and Hydrogen 24 5. From this analysis Mr. P. proceeds to give a comparative estimate of the composition of the Prussic acid, of the ferruretted and sulphuretted chyazic acids, and of their respective salts, as deduced from experiments, and inferred from the atomic theory, of which a tabular view is given. Mr. P. infers from the whole that the composition of these acids and their saline combinations, is in perfect accordance with the atomic theory, and not incompatible with the opinion that azote is a compound body.

On the Nature and Combinations of a newly discovered vegetable Acid; with Observations on the malic Acid, and Suggestions on the State in which Acids may have previously existed in Vegetation By M. Donovan, Esq.

This acid, to which Mr. Donovan has given the name of Sorbic acid, is obtained in rather large proportions from the ripe fruit of the Sorbus Aucuparia, though it is not confined exclusively to that fruit. When perfectly pure, it is transparent, fluid, and inodorous, soluble in alcohol, and in any proportion in water. When evaporated, it becomes an uncrystallizable solid mass, but deliquescent. If subjected to distillation, no part of the acid passes over in the process. Its acidity is such as to cause a painful sensation upon the tongue. It is little changed by being kept in an uncombined state. In those fruits in which it exists mixed with malic acid, it is the first to disappear, while the malic acid retains its distinctive properties long after the commencement of decay in the plant. The saline combinations which this acid forms, sufficiently distinguish it from the other vegetable acids, and especially from the malic with which it is generally found co-existent. With lead it forms three saline combinations, a super, a neutral, and a sabsalt. The super-sorbate does not assume the solid form, but the neutral and subsorbate acquire more than 5000 times their weight of water for their solution. With potash, soda, and ammonia, when the acid is in excess, it forms permanent crystals which are soluble in water, but insoluble in alcohol. The malic acid forms with these bases, salts which are deliquescent and uncrystallizable. With the earthy carbonates, the sorbic acid forms neutral salts

which are precipitated as soon as they are formed. With alu mina it does not appear to have any action, and hence Mr. D. thinks it may probably prove a valuable agent in the hands of the analytic chemist, to obtain this earth perfectly pure. Mr. D. observes that this acid is never found in any mature fruits which contain any other acid than the malic; that the malic acid is never found alone in any mature fruit, but always accompanied with the sorbic, and that these two acids when co-existent exclude every other. The fruits which contain these acids together, are apples, plums, the berries of the sorbus, barberries, and sloes; of these the sorbus berry contains the largest quantity of sorbic acid, unripe apples less, ripe apples and sloes still less, barberries very little, and plums least of all. As the discovery of the general co-existence of this acid with the malic, renders Scheele's process for procuring malic acid, liable to considerable obj ction, Mr. D. recommends the general adoption of Vauquelin's process for obtaining it from the juice of the Sempervivum Tectorum, in which this acid exists alone, in a state of combination with lime; but as there is some difficulty in completely decomposing the malate of lead by sulphuric acid, he suggests the employment of sulphuretted hydrogen, to remove the last portions of lead, by which means the malic acid is obtained perfectly pure. Mr. D. thinks it probable that the vegetable acids are not formed primarily by the immediate combination of their elements, but by the combination of oxygen with the bitter principle, and the facts which he has adduced give considerable probability to this view of their origin.

On the Structure of the Organs of Respiration in Animals which appear to hold an intermediate Place between those of the Class Pisces, and the Class Vermes, and in two Genera of the last mentioned Class. By Sir Everard Home Bart. V.P.R.S.

Descriptions of anatomical structure, whether human or comparative, are for the most part so little intelligible without the aid of preparations, or engravings, that no apology we presume will be necessary for our simply transcribing the titles of this, and the following paper.

On the Mode of Generation of the Lamprey and Myxine. By Sir Everard Home, Bart. V.P.R.S.

An Account of some Experiments with a large Voltaic Battery. By I. G. Children, Esq. F.R.S.

The battery with which these experiments were performed, is composed of plates of 6 feet in length by 2 feet 8 inches in breadth, so that each plate has a surface of 32 square feet, and each surface of the zinc plate has a plate of copper opposed to

it, so that each cell of the battery (21 in number) contains one zinc and two copper plates. This addition of a plate of copper to each surface of zinc, was made at the suggestion of Dr. Wollaston, and was found to augment the power of the battery very considerably The experiments detailed in the communication, rela.e principally to the power of the battery in igniting different metallic wires when placed in the electrical circuit, and its effect in fusing some of the more refractory substances. Its effect in producing ignition, was estimated by placing two pieces of wire of dissimilar metals, but equal in length and diameter, so as to make them form part of the circuit. The length of each wire was eight inches, and the diameter of an inch. Wires of platina and gold being brought into the circuit, the platina was ignited, the gold not; with gold and silver wires, the gold was ignited the silver not; with gold and copper wires, both were equally ignited; with gold and iron, the iron was ignited the gold not; with platina and iron both were ignited, but the iron more intensely than the platina; with platina and zinc, the platina was ignited, the zinc not, but melted at the point of contact; with zinc and iron, the iron was ignited, the zinc neither ignited nor fused; with lead and platina, the lead fused at the point of contact, but neither was ignited; with tin and platina, no ignition of either wire, but the tin fused at the point of contact; with zinc and silver, the zinc became ignited and then melted, the silver being unchanged. The results were the same to whichever pole of the battery either wire was presented. When the experiments were repeated with several alternations of different wires the results were also the same. The hypothesis which Mr. C. offers in explanation of these phenomena, is founded on the supposition that the effects of Voltaic electricity, whether chemical or in producing heat and ignition, depend on the resistance which it meets with in its transmission through bodies; and hence, in being transmitted through wires of different metals, the conducting power of each will be in the inverse ratio of the effect of the electrical current in producing ignition. The substances exposed to the action of the battery with a view to their fusion, were chiefly the oxides of the more refractory metals, as tungsten, tantalum, uranium, titanium, cerium, molybdena, iridium, and osinium; most of these were fused and some of them reduced. It did not fuse the ruby, or sapphire, nor quartz, silex, nor plumbago. On the suggestion of Mr. Pepys, some diamond powder was heated by the battery in contact with a wire of pure soft iron; the diamond disappeared, and the wire was converted into perfect steel, though the ignition was far from being intense, and was kept up for six minutes only. The surface of the wire which had been in contact with the diamond had fused, and had

run into numerous small cavities. This experiment may be considered perfectly conclusive, as to the nature of diamond, and the conversion of iron into steel. Of two equal portions of mercury placed in communication with the opposite poles of the battery, and connected together by platina wire, that connected with the zinc end was heated to 121° in twenty minutes, and the other to 112°. The battery in its most active state, gave no charge to a Leyden phial. When the plates of each metal were so connected, as to reduce the whole battery to a single pair of plates, each presenting a surface of 1344 square feet, and suspended quite out of the contact of the acid liquor in the cells, there was not the slightest appearance of ignition in an extremely fine platina wire ( of an inch diameter, and of an inch in length) by which the communication was made between the two surfaces; though Dr. Wollaston has ascertained that a wire of the same dimensions is instantly ignited by a single pair of plates of one inch square on their being immersed in a diluted acid.

Some additional Experiments and Observations on the Relation which subsists between the nervous and sanguiferous Systems. By A. P. Wilson Philip, Physician in Worcester.

The title prefixed to this paper does not convey an accurate idea of its nature, for no inconsiderable portion of it is occupied by an investigation of the different phenomena which are presented by stimuli applied to the brain and nervous systems, as they refer to the muscles of voluntary and involuntary motion. The first series of experiments relate principally to this subject, and Dr. P. has thus concisely stated the results which he obtained. It appears from these experiments, that chemical stimuli, applied to the nervous system exert a greater power over the heart than mechanical stimuli, while the latter exert a 6 greater power over the muscles of voluntary motion than chemical stimuli; that both chemical and mechanical stimuli, applied to the nervous system, excite the heart, after they cease to produce any effect on the muscles of voluntary mo< tion; that stimulating every part of the brain and spinal marrow equally affects the action of the heart, while the 'muscles of voluntary motion are only excited by stimuli applied to those parts of the nervous system from which the 6 spinal marrow and nerves originate; that stimuli applied to the nervous system never excite irregular action of the heart, while nothing can be more irregular than the action they excite in the muscles of voluntary motion; that their effect on these muscles is felt chiefly on their first application, but con'tinues on the heart as long as the stimulus is applied.'