292 



Major W. A. Ross on Jeypoorite. [May 15, 



of later observations made under much more favourable circumstances 

 was v=292-4:X 10 8 centims. per second. 



The latest observations (1872) furnish the most probable value of v, 

 293 x 10 s centims. per second. 



II. " On Jeypoorite, a Sulph-antimonial Arsenide of Cobalt." By 

 Major W. A. Ross, late Royal Artillery. Communicated by 

 Prof. W, H. Miller, Foreign Sec. R.S. Received April 16, 

 1873. 



A mystery has pervaded the history and character of this almost un- 

 known mineral (the very name of which is mis-spelled " Syepoorite "), 

 which was scarcely to have been expected from English mineralogists, as 

 the only place in the world in which it has yet been found is the copper- 

 mines of Khetree, in the Hindu principality of Jeypoor, in Rajpootana, 

 India, the Rajah of which territory politely sent the writer the specimens 

 of which an analysis is here submitted. 



Notwithstanding Jeypoor is one of the feudatories of the British 

 Grovernment of India, it is believed that there is not a specimen of this 

 mineral in the British Museum ; at any rate there was not one in 1868, 

 when Professor Maskelyne even expressed to the writer his doubt of the 

 existence of such a mineral. 



Professor Mcol (' Manual of Mineralogy,' p. 458) tells us (1849) that 

 this mineral, which he calls " Syepoorite," from " Syepoor near Raj- 

 pootana"! was analyzed by Middleton, who found in it 64-64 per 

 cent, cobalt and 35*36 sulphur*. Dana and other mineralogists have 

 followed this account ; and Professor Miller informs me that Middleton's 

 analysis is given in the ' Memoirs of the Chemical Society,' vol. iii. 

 1845-48, p. 39. There may, of course, be a mineral from the same place 

 answering the description of Middleton's analysis. All I assert is that 

 none of the many crystals examined by me gave the indications of a 

 pure sulphide of cobalt. At first I certainly thought Jeypoorite was 

 only an antimonial sulphide of cobalt, not having any reason to doubt 

 further the description given by Nicol ; but by a closer and novel method 

 of examination, to be presently described, I succeeded in detecting arsenic 

 in considerable quantity. 



Plattner (' Probirkunst mit dem Lothrohre,' vierte Auflage, Leipsic, 

 1865) attributes to Jeypoorite, evidently from the description of another 

 work, a percentage of 65*2 cobalt, with the remainder sulphur, and says 

 of it, at p. 311, "Das Lothrohrverhalten ist nicht bekannt." 



* If Middleton had found iron, copper, &c, one might have supposed that he took 

 some of the general sand for his analysis, which would of course reduce the percentage 

 of cobalt and raise that of sulphur. 



