In an experimental inquiry into the action of water on lead, published by me in 1829, in continuation of some previous researches by Guyton-Morveau, it was stated as the general result, that all very pure waters, such as distilled water, rain, and melted snow, act upon lead,—dissolving a trace of it, and causing the formation of an insoluble carbonate of lead in large quantity. It was like-wise shewn, that this action is prevented by the existence of neutral salts in solution; so that most terrestrial waters, as they contain saline matter, act feebly and only in circumstances favourable in other respects. Farther, it appeared to flow from comparative experiments, that this preventive power depends upon the acids of the salts, and not upon their bases;—and that their energy as preventives, that is, the minuteness of the proportion required to annihilate the action, is in the ratio of the insolubility of the compounds which the acids of the salts are capable of forming with oxide of lead.

That the eggs of numerous parasitic animals may be deposited in the textures of living beings, and that these develop themselves in such textures, and draw thence their nourishment, has been long known. But that, under particular circumstances, certain cryptogamic plants are capable of germinating and fructifying in the living tissues of animals, and especially in man himself, is a discovery of recent date.

Malpighi was the first to announce that all secreting glands are essentially composed of tubes, with blind extremities. Müller, by his laborious researches, has brought this department of the anatomy of glands to its present comparatively perfect condition. Purkinje announced his hypothesis of the secreting function of the nucleated epithelium of the gland ducts, but made no statement to shew that he had verified it by observation. Schwann suggested that the epithelium of the mucous membranes might be the secreting organ of these surfaces. Henle described minutely the epithelium cells which line the ducts of the principal glands and follicles, but did not prove that these are the secreting organs. The same anatomist has stated, that the terminal extremities of certain gland ducts are closed vesicles, within which the secretion is formed, and which contain nucleated cells. Henle has not, therefore, verified the hypothesis of Purkinje, although he is correct in stating that the terminal vesicles of certain gland ducts are closed. It will be shewn, in the course of this paper, that the secretion is not formed, as Henle has asserted, in the closed vesicles, but in the nucleated cells themselves.

To all those who have paid any attention to the subject of quarantine, it is well known that certain articles are held to be susceptible of conveying the contagion of plague; that certain others, in regard to this property, are considered doubtful; and that others are held to be unsusceptible of retaining and communicating it.

Are these distinctions accurate? Are they founded on well-established facts? On these questions I shall have the honour of submitting some remarks to the Society, with the hope of drawing attention to a subject of much importance, and hitherto, in a scientific point of view, strangely neglected.

The subject of the following Memoir has been already touched on in a communication which I made to the Cambridge Philosophical Society, and which appears in the seventh volume of their Transactions, Art. IX. For the better understanding of what follows, it is desirable to state briefly the contents of that paper. Its object is to estimate the quantity of light which is received on a screen of unlimited dimensions, after passing through a certain aperture, or suffering reflection at two mirrors, as in the case of the interference experiment, so as to exhibit the appearance of bands.

The minerals of the zeolite family have for many years attracted the especial attention of men of science, and the class has been rapidly extended in proportion to the progress made in its study in a crystallographic as well as chemical point of view. The first characteristic difference, originally observed long since by Cronstedt, and by him considered to be the distinguishing mark of one single mineral species, which he designated Zeolite,—namely, the property of swelling out by heat previous to fusion,—has since been found to belong to a great number of other combinations. These, although materially different from each other in crystallographic form, have proved to be closely allied in chemical constitution, in so far as they consist, without exception, of a silicate of an alkali or alkaline earth, in combination with a silicate of alumina and water. It is evident, then, that the relation of the silicic acid to the base, in both terms, as well as the quantity of water, is capable of considerable variation, so that the general niineralogical formula which should embrace all the members of the zeolite family would be

Where r represents the monatomic alkaline or earthy basis, and the terms u, t, ,T, y, and z, are capable of varying within certain limits.