138 



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. 



Analysis of a triple Sulphuret, of Lead, Antimony, and Copper, from 

 Cornwall. By Charles Hatchett, Esq. F.R.S. Read January 26, 

 1804. [Phil. Trans. 1804,;?. 63.] 



This is the analysis to which the Count de Bournon 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. 

 With some Remarks on the Structure of those Orifices ; 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,;?. 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 



