scribed, and that many of those with which we are acquainted have
not been sufficiently examined.
A general observation, which he tells us is founded upon long ex- perience, is, that there exists a great variety of minerals which have the same substance, or collection of substances, for their basis, and are combined with the same modifying substance, but whose differ- ences arise merely from the variety of proportions in these bases or substances.
The paper closes with an earnest exhortation to those who culti- vate mineralogy, to choose for the subjects of their experiments a variety of perfect specimens from different districts, and as much as possible from different matrices: that they make a number of com- ' parative analyses; and that the mineralogist and the chemist mutually sanction the operations of each other in their respective departments.
This is the analysis to which the Count de Boumon more than once refers in his elaborate account of the same mineral, lately read to the Society. We find here, in addition to the information con- tained in that paper, that one of the reasons why this very scarce ore has been hitherto so little attended to, is probably its great resem- blance to an ore of antimony; that by all the chemical tests by which it has been tried, its constituent parts are manifestly lead, antimony, copper, and a small proportion of iron, the whole combined with sul- phur; and that when the specific gravity, the external and internal colour, the fracture, the grain, and other characters here described are considered, there can be no doubt that the three first metals exist in the ore in, or nearly in, the metallic state, combined with sulphur, so as to form a triple sulphuret. The proportion of the in- gredients are as given by Count de Bournon, who, in fact, took them from this paper.
Observations on the Orifices found in certain poisonous Snakes, situated between the Nostril and the Eye. By Patrick Russell, M .D. F.R.S. PVith some Remarks on the Structure of those Orific‘es; and the Description of a Bag connected with the Eye, met with in the same Snakes. By Everard Home, Esq. F.R.S. Read February 2, 1804. [Phil Trans. 1804, 11. 70.]
The orifice, which is the principal object of this paper, has been long since noticed by naturalists, who conceived it to be the external organ of hearing. Dr. Russell, in the many opportunities he has had of observing a variety of snakes, has particularly examined them with respect to this feature: and he here informs us, that he has found in the whole class (exclusive of the rattle-snake) fifteen or
