458 J. W. Richards—" Mohawkite." 



correspondence is still closer. I have re-calculated Ledoux's 

 results, as follows : 



Atomic ratios. 



Copper 68-6 1-082"! 



Cobalt 1-2 0-020 I 



Nickel... 6-55 0-112 \ l Jib 



Iron 0-23 0-004 J 



Sulphur 0-53 O'Ol'Z 



Arsenic 22-67 0*302 



Assuming the sulphur to be present as RS, we subtract its 

 ratio 0*017 from that of the bases, and there remains 1*201. 



Ledoux's ratio is, therefore, == 3-98. 



' ' 0-302 



I would propose the name Ledouxite for the compound 



Cu 4 As, the existence of which no longer appears doubtful. It 



carries small percentages of cobalt and nickel and is similar in 



appearance to algodonite, with density 7*8 (Ledoux) or 8*07 



(Richards). The latter was taken on clean material free 



from gangue. 



Mineralogical Laboratory, 



Lehigh University, April 5, 1901. 



