phosphorus, placed in other circumstances, would absorb the same quantity of oxygen, or whether in fact there were not other phosphoric acids. The action of chlorine was employed for this purpose; and the result was that, according to the estimate founded upon this process, 100 parts of phosphorus require 123 parts of oxygen, to be converted into phosphoric acid, so that we are justified in concluding that the acid produced by the medium of chlorine, is exactly similar to that produced by nitric acid.

It has already been observed that Sir H. Davy gives a different statement respecting the constituents of phosphoric acid: he conceives that 100 parts of phosphorus require 150 of oxygen, and that the phosphoric requires twice as much oxygen as the phosphorous acid. As his calculation depends upon the idea which he entertains concerning the constitution of the chloruret of phosphorus at the maximum, or the perchloride of phosphorus, it appeared necessary to examine this substance. For this purpose a vessel was filled with chlorine, the weight of which was ascertained; into the same vessel, after removing the chlorine, a minute quantity of phosphorus was introduced, and it was again filled with chlorine, by which means the phosphorus was immediately converted into the perchloride; and by ascertaining the addition of weight acquired by the vessel, it was calculated that 100 parts of phosphorus were united with 549·1 of chlorine ; Sir H. Davy's estimate makes the latter number 666. As it had been before found that the chloruret at the minimum, or the protochloride, was composed of 100 parts of phosphorus to 347-7 parts of chlorine, and as 347-7 is to 549-1 very nearly in the ratio of 3 to 5, we may conclude that the oxygen of the phosphorous acid, is to that of the phosphoric in the same ratio, instead of that of 1 to 2. Phosphoric acid must then be composed of phosphorus 44-48 parts, and oxygen 55.52 parts; or phosphorus 100 parts, and oxygen 124.8 parts.

A remarkable phenomenon is mentioned as taking place from the decomposition of the chloruret of phosphorus by water. If a piece of this substance is projected upon water, the violent heat which is evolved reduces the greatest part of the chloruret into vapour. If, on the contrary, the chloruret in powder is thrown upon water, not much heat is excited; but an oleaginous fluid is formed, which soon begins to act upon the water, a great increase of temperature ensues, and the oily body disappears. This oily matter was collected in a separate state, and submitted to a number of experiments, which showed it to be different from either of the chlorurets; but it is conceived to be rather a union of several bodies, than a specific compound. What appears the most probable, is, that it is a hydrate of the chloruret of phosphorus, holding in solution a large quantity of this same chloruret.

When phosphorus is burned in oxygen, or in atmospherical

air, with an excess of oxygen, or of air, the acid which results is pure phosphoric acid, without any addition of phosphorous acid. Dr. Thomson adopted this method of analyzing the acid, and obtained results nearly similar to those mentioned above. The properties of the phosphoric acid, which forms a component part of the bones of animals, appeared to possess properties exactly similar, so far as regards the formation of salts, and its capacity for saturation. It is necessary to observe that the phosphoric acid, which is obtained by the calcination of the phosphate of ammonia, is not pure, as it is impossible to remove the whole of the ammonia from it. A quantity of water still adheres to phosphoric acid, although it is kept for a long time in a state of fusion; and this is estimated at 20-6 parts in 100 parts of the acid, which is equivalent to 18-2 parts of oxygen, almost exactly the third part of the whole which is contained in phosphoric acid.

With respect to the composition of the phosphates, M. Dulong's analyses do not agree with either those of Professor Berzelius, or Dr. Thomson: the salts which Berzelius examined are supposed not to have been in the neutral state; and Dr. Thomson has not completed his examination of these bodies, so that the subject may still be regarded as requiring further examination. Three points, however, seem to be ascertained; 1. that the neutral phosphites are changed into phosphates without having their neutrality destroyed; 2. that the hypophosphites, by the same process, yield an acid phosphate; 3. that the metallic phosphurets, obtained by the process mentioned above, are, in reality, merely proto-phosphurets, corresponding to the protoxides which are combined with acids. With respect to the weight of the atom of phosphorus, it is stated to be 20-03, that of oxygen being taken as 10; as phosphoric acid is composed of two atoms of phosphorus and five of oxygen, it will be represented by 90-06.

It appears from the above statement respecting phosphorus, that the analogy which it bears to sulphur is not so great as has been generally conceived. The proportions in which phosphorus and oxygen unite are more analogous to those of azote and oxygen; and the composition of the phosphates and phosphites has also a strong analogy to those of the nitrates and nitrites. On the other hand, it is to be observed that phosphorus and azote differ from each other, as much as possible, with respect to their combustibility.

ARTICLE XIV.

ANALYSES OF BOOKS.

Philosophical Transactions for the Year 1817, Part II.

(Concluded from p. 58.)

IT has been long known that the Island of Java contains a peculiar species of swallow, the nest of which is composed of an animal substance; but naturalists have never been able to ascertain the source from which it is derived, nor the materials of which it is formed. Several circumstances, however, seemed to prove that it proceeded from the stomach of the animal itself; and this induced Sir Everard Home to examine the digestive organs of this peculiar kind of swallow, and to compare them with those of other species of the same genus. The author was informed by Sir Stamford Raffles, late Governor of Java, that the swallows, peculiar to that island, do not migrate; they spend a considerable part of the day in the neighbourhood of extensive swamps, that abound with various kinds of insects, and retire, at the close of the day, to large caverns, which they inhabit in prodigious numbers. The bird is double the size of our common swallow the male and female lie in separate nests, each adapted to their form, the female nest being wider and deeper, in order to receive the eggs.

By comparing together the gastric glands of the Java swallow, the common swallow, and the black-bird, the peculiar structure of the first was sufficiently obvious. According to the description, "there is a membranous tube surrounding the duct of each of the gastric glands, which, after projecting into the gullet for a little way, splits into separate portions like the petals of a flower." In the examination of the parts, the author received the assistance of Mr. Bauer, who has given us exact representations of what he detected by his microscope. It is reasonable to conclude that these peculiarly formed tubes secrete the animal matter of which the nests are composed, although we have no means of judging how the process is conducted.

This provision, which the Java swallow possesses, of forming a nest from its own secretions, is a remarkable anomaly among the higher order of animals; it is said by the author to prove that this bird was intended by nature to be an inhabitant of the island of Java," in which nothing is to be met with out of which a nest could be constructed;" but we are not informed in what this deficiency of materials consists, or upon what it depends. Mr. Brande examined the substance, and found it to have "properties intermediate between gelatine and albumen; the quantity of gelatine, however, appears to be very minute, so

"

as scarcely to account for the difference between this substance and common albumen.

1

In consequence of the discovery of these peculiarly formed gastric glands in the oesophagus of the Java swallow, Sir Everard Home requested Mr. Bauer to examine the structure of the external membrane of the oesophagus and stomach in the human subject. It was found that the "œsophageal glands, when examined in the microscope, have the appearance of infundibular cells, whose depth does not exceed the thickness of the membrane." The structure of these glands somewhat resembles that of the same parts in birds, and, like them, possesses the exclusive property of coagulating milk. Mr. Bauer found that the structure of the upper arch of the stomach is "made up of cells in the form of a honey-comb, the sides of which are not formed by the doubling of the membrane (for no stretching of the cells alters the form of their orifices), but are regular partitions constructed between the cells." This same structure is found, only in a less distinct form, over the whole of the cardiac portion of the stomach. In the pyloric portion there is also the same kind of cells; but in addition to the former structure, "there are small clusters, the sides of which rise above the surface, giving the appearance of foliated menabranes." This foliated structure is still more considerable in the duodenum. From his examinations the author is led to conclude that the gastric glands in the human stomach are, in proportion to its bulk, considerably smaller than in most other animals.

The conclusion that is deduced from these observations is, that there are three different kinds of organization employed, in adding to the food three different ingredients, which are requisite for its conversion into a material that can be assimilated with living animal matter, and be employed in carrying on the functions of life, also supplying the waste which is constantly taking place. The most important of these is evidently the gastric glands; next in order may be considered the honeycomb structure, and least so, although by no means unnecessary, the foliated membranes, which we know, from what takes place in the Java swallow, form the mucus that is mixed with the other ingredients."

In the conclusion of his paper, Sir Everard Home takes occasion to give an account of a human stomach, which was found after death divided into two portions, by a firm contraction of its substance, which, he conceives, affords an illustration of the healthy state of the stomach while the process of digestion is going forwards.

The species of Sepia inhabiting the shell of the Argonauta Argo has, by all ancient and by most modern naturalists, been considered as the proper animal of the shell. A few eminent naturalists of the present day have, however, supposed that the animal hitherto found in this shell is parasitical. This opinion

has derived its strongest support from the absence of those organs on the surface of the body of the animal in question, which are found in all the shelled mollusca, and by which the secretion of the calcareous matter forming the shell is effected. Rafinesque, from his situation on the coast of the Mediterranean, has had peculiar opportunities of studying this animal, and is fully of opinion that it belongs to a genus nearly allied to the sepia of Linnæus, to which he has given the name of ocythöe, and resides, parasitically, in the above-mentioned shell.

Some observations made by the late Mr. Cranch, zoologist to the unfortunate expedition to the Congo, tending strongly to confirm the theory of Rafinesque, are detailed by Dr. Leach in the present paper.

"In the Gulf of Guinea, and afterwards on the voyage, he took (by means of a small net, which was always suspended over the side of the vessel) several specimens of a new species of ocythöe, which were swimming in a small argonauta, on the surface of the sea.

Two living specimens being placed in a vessel of sea-water, the animals very soon protruded their arms, and swam on and below the surface, having all the actions of the common polypus of our seas. By means of their suckers they adhered firmly to any substance with which they came in contact; and when sticking to the sides of the basin, the shells might easily be withdrawn from the animals. They had the power of completely withdrawing within the shell, and of leaving it entirely. One individual quitted its shell, and lived several hours, swimming about, and showing no inclination to return to it; and others left the shells as he was taking them up in the net."

The same species which has furnished Dr. Leach with the materials for this paper, has also afforded to Sir Everard Home the subject of a short communication, tending to confirm the opinion of Rafinesque. In some of the specimens of ocythöe cranchii, the animal had deposited its eggs in the involuted part of the shell which it occupied; these eggs form a cluster, held together by pedicles, one of which belongs to each egg, in this respect resembling the ova of the sepia octopus. But the eggs of all the testaceous aquatic mollusca, as far as they are known, are enveloped in a gelatinous mass, which corrugates by the action of the sea water, and thus encloses each ovum in a cell, in which the young animal passes the interval, usually very short, between its being excluded from the membranes of the ovum, and its acquiring a shell.

Dr. J. R. Johnson, of Bristol, has communicated some observations on the hirudo complanata, and hirudo stagnalis, the object of which is to show that these animals differ from the other known species of leech in such important characters as to justify the arrangement of them in a new genus, to which Dr. J. gives the name of glossopora.