CHEMISTRY. 225 



total amount thus accounted for is $500,000,000. Over $300,000,000 have 

 been actually put upon the market, and nearly $100,000,000 more have 

 probably been lost in tailings. Tlie low-grade quartz not extracted most 

 likely contains more than another hundred millions, but the sum obtained 

 by calculation is nevertheless a fair approximation to the amount which the 

 Lode must actually have contained. On the other hand, if an attempt be 

 made to account for the ore on any other supposition than that it was derived 

 from the diabase, it seems very difficult to give a plausible explanation for 

 tlie disappearance of the gold and silver which appear to have been extracted 

 from tliis rock. 



Other rocks. — The diorite also contains precious metals; but while dioritic 

 vein matter is highly charged, and even tliat at the mouth of Bullion ravine, 

 which is very solid but contains some pyrite and is very close to the Lode, 

 carries a notal)le quantity, that from the head of the same ravine shows only 

 a trace of silver. These relations are the reverse of those observed in the 

 diabase and appear to indicate an impregnation from the Lode. The diorite 

 also contains a trace of gold. More could hardly have been ex])ected ; for, 

 except on Cedar Hill, it has never been found worth while to treat the gold 

 quartz of the District, and the Cedar Hill mines have yielded but little. 



The andesites and the quartz-porphyry show only very small amounts 

 of silver, but the metamorphic diorite contains eight cents per ton. The 

 analysis also shows that this rock is highly calcareous, and it seems not 

 impossible that the Justice ore body, which is associated with the meta- 

 morphic diorite, was derived from it. The basalt, on the contrary, is 

 nearly as rich in silver as the older diabase, but no ore is likely to have 

 been extracted from it, for the rock is not only the freshest in the Distkict, 

 but is remarkably fresh for any region, many of the olivines showing no 

 trace of attack. 



Lateral-secretion theory affirmed. Ou tllO wliolc, thercforC, tllC cheillical aud gCO- 



logical evidence point to the late)-al-secretion theory as tlie true explanation 

 of the Washoe ore deposits, and to the augite of the older diabase as the 

 source of the important ore bodies. It is worth while to note that, accord- 

 ing to report, many of the famous silver mines of the world are associated 

 with this rock. 

 15 c L 



