No. 1.] WRIGHT — GASES IN SMOKY QUARTZ. 15 



described in a succeeding paragraph, gave a somewhat different 

 result. 



The rock when broken or crushed with a hammer exhales a 

 fugitive but unmistakeable odor of hydrogen sulphide, but the 

 proportion of the gas was too small to be directly detected with 

 the ordinary lead-paper even when directly applied as a cover to 

 a diamond mortar in which a considerable quantity of the material 

 had been powdered. But when a slip of the paper was introduced 

 into a tube filled with the extracted gases, a slight but distinct 

 coloration was produced. The same was true in a somewhat 

 more marked degree with a paper moistened with mercurous 

 nitrate, indicating sulphurous oxide. To test this more fully 

 separate slips of filtering paper were wet with plumbic acetate, 

 sodium nitro-prusside, and mercurous nitrate. When dry they 

 were introduced into a small tube through which gas freshly 

 liberated was made to pass. Snow applied for a few moments to 

 the tube ensured the presence of sufficient water to moisten the 

 paper slightly. The first underwent a slight discoloration, which 

 after a time disappeared, the second assumed a pinkish tint, while 

 the third was distinctly blackened, thus proving the presence of 

 a trace of both the gases in question, a conclusion moreover which 

 was verified by other and independent trials. 



As both hydrogen sulphide and sulphurous oxide are absorbed 

 by potasssic hydrate it was important to ascertain whether these 

 gases were in sufficient quantity to affect the conclusion given 

 above as to the amount of carbon dioxide. A portion of the gas 

 collected in a clean tube was therefore submitted to a special 

 examination. A pellet of ferric oxide formed upon the end of 

 a platinum wire produced no effect at all, though kept in the gas 

 for several hours. A similar pellet of manganese dioxide moist- 

 ened with syrupy phosphoric acid likewise caused no perceptible 

 effect, thus proving that these gases were not present in any 

 measurable quantity. 



An approximate estimation of the amount of water was made 

 as follows : The U- tubes in which the water had been condensed 

 were sealed after the gas had been thoroughly pumped out. The 

 temperature of the freezing mixture was from — 19^ to — 20'^ C, 

 so that the tension of the residual vapor was less than one milli- 

 meter, which was confirmed by the reading of the guage of the 

 pump at the end of the operation. The connecting tubes were 

 fused off and the portion containing the water withdrawn. The 



