of some of the Cornish Mines. 365 



Nitrogen 83- 146 per cent. 



Oxygen 16-764 



Carbonic acid 0*090 



Sulphuretted hydrogen . . . strong trace. 



100-000 

 Sample 12. One gallon. 

 Cam Brea. — Copper mine, granite. Immediately after 

 firing a hole; from the 105-fathom level from surface, and 

 twenty-five fathoms from any winse or shaft; two men in a 

 core; specific gravity '994. 



Oxygen. 

 Average of two experiments with hydrogen .... 16*72 

 Average of three experiments with nitrous gas . . . 16'66 

 Average of three experiments with quadrisulphuret 1 . . 

 of lime J 16 ' 70 



Mean . . . 16*693 



Carb. acid. 

 Average of four experiments with lime water and 1 



solution of potash J 



Composition of sample : — 



Nitrogen 83*237 per cent. 



Oxygen 16*693 



Carbonic acid . . . 0*070 



100*000 

 Sample 13. One gallon. 

 Cam Brea. — As before. 95-fathom level, machine blowing 

 air; two men in a core; spot wrought only sixteen hours out 

 of the twef?ty-four ; sample taken three quarters of an hour 

 after firing a hole ; specific gravity 992. 



Oxygen. 

 Average of three experiments with hydrogen .... 14*50 

 Average of two experiments with nitrous gas .... 14-64 

 Average of three experiments with quadrisulphuret"! 

 of lime J 



Mean . . . 14*51 



Carb. acid. 



Average of three experiments with lime water .... 0*12 



Average of three experiments with potash solution . . 0*14 



Mean . . . 0*13 

 Composition of sample : — 



