1823.] Geological Transactions of Cornwall f Vol, I L 55 



in Grwennap. I had desired a workman employed at the stamp- 

 ing-mill and burning-house at Both^rris, to send me three speci- 

 mens of tin ore containing copper, one of which I found to be 

 an aggregation of yellow copper ore and tinstone ; another of 

 grey copper ore and tinstone ; but the third, to my great sur- 

 prise, had a compact uniform structure, perfectly homogeneous 

 in appearance, resembling tin pyrites in all its external characters ; 

 and on comparing it with the specimens in our cabinet, it agreed 

 in every respect, except that its colour was a little lighter, with 

 rather more of metalhc lustre. To determine its nature with 

 greater certainty, liiis substance was submitted to the following 

 experiments : When exposed to a red heat in a covered crucible, 

 it lost weight, and sulphur was sublimed : calcined with free 

 admission of air, sulphurous acid gas was evolved ; it increased 

 in bulk ; changed to a dark-brown colour, and lost 15 per cent, 

 in weight. In nitromuriatic acid it readily dissolved without the 

 application of heat, and during solution, nitric oxide gas was dis- 

 engaged. Intending subsequently a more accurate analysis, a 

 rough one was performed after the method proposed by Klaproth. 

 The result was, in 100 parts : 



Copper 31 



Tin 28 



Iron 6 



Sulphur 25 



I Silica, with a little alumina 7 



^ Loss 3 



Too 



The loss was probably occasioned by some of the sulphur 

 (during the solution of the mineral in the acid) escaping in the 

 form of sulphuric acid gas. This analysis proves beyond doubt 

 that the mineral was tin pyrites." 



Dr. Boase was unable to procure even another specimen of 

 this mineral from Botallack ; but it appears that the one just 

 described came from that part of the mine which is called Huel- 

 Hazard. 



XX. On the Temperature of the Cornish Mines, /By M. P. 

 Moyle, Esq. MGSC. 



XXI. On the Serpentine District of Cornwall. By the Rev. 

 John Rogers, MGSC. 



This paper, hke the former one by the same author, consists 

 of local details unsusceptible of abbreviation : they are chiefly 

 confined to some circumstances of the interesting district in 

 question, which, Mr. Rogers states, have escaped the notice of 

 Mr. Majendie and of Prof. Sedgwick, in their respective surveys 

 of it. 



A series of tables of the quantities of tin and copper raised 

 in Cornvvajil in different years, those of the former metal coii)i- 



