354 Mr. G. W. Keely on a new Attempt to determine the 



The result of this analysis differs but very little from the com- 

 position of specimens of this mineral from other localities, to 

 which the formula 4(Cu 2 , Ag, Fe, Zn, Pb) S, Sb S 3 is attributed ; 

 it appears not unlikely, however, that in such metallic sulphosalts 

 the copper may really be present as CuS. Taking the actual 

 amounts of the metals found by this analysis and representing 

 them as sulphides, the numerical results in both these cases will 

 be as follows : — 



Sulphide 



of antimony, 



SbS 3 



34-82 . . 34-82 



)) 



silver, 



As>-S , 



15-67 .. 15-67 



)) 



copper, 



Cu 2 S 



28-51 CuS 34-26 



}) 



iron, 



PeS 



7-57 . . 7-57 



)> 



zinc, 



ZnS 



7*18 .. 7-18 



)3 



lead, 



PbS 



1-66 . 1-66 



95-41 



101-16 



The minerals associated with this specimen were galena, chal- 

 copyrite, iron pyrites, zincblende, quartz, dolomite, chalybite, and 

 calcite. 



The lode itself cuts through both the Lower Silurian (non- 

 f ossiferous) slates and the eruptive granite, which latter made 

 its appearance subsequently to the deposition of these beds. 



This granite is identical in mineralogical composition with the 

 auriferous granites of other parts of the world, being composed 

 of orthociase, Muscovite, and quartz ; and traces of gold are re- 

 ported to have been found in the gullies containing its debris, as 

 well as in the quartz veins which are found in the slates in close 

 proximity to it. 



XL1IL A new Attempt to determine the Resultant of two Pres- 

 sures on a Fixed Point. By G. W. Keely, Esq.* 



rjpilROUGH the vertices A, B, D, of a triangle which is the 

 Jl half-base (right-angled at D) of a right square pyramid, 

 let the directions of three forces, 

 p, q, r, pass respectively, the 

 forces being applied at the ver- 

 tex of the pyramid. The total 

 resultant will pass through some 

 point G, determined by drawing 

 in the plane of the base two 

 straight lines from A and B, to 

 the points L and P, through which are assumed to pass the re- 

 sultants of q and r and of p and r • and a third line, drawn 



Communicated by the Author. 



