turbance early in the Cretaceous and a more gentle uplift at a 
later date. This relation is not unnatural. The primary condi¬ 
tion for the formation of veins of ore is that fissures should exist, 
and these are naturally most plentiful where disturbances have 
been most profound Moreover the deposition of ores, at least 
in a very large proportion of cases, is dependent upon heated 
waters containing various powerful chemicals such as sometimes 
accompany or follow volcanic outbursts. But volcanic rocks are 
also most frequently and most naturally found where deep fissures 
establish a connection between the surface of the earth and the 
profound depths from which lavas emanate. All of the great 
lines of uplift show abundant traces of former volcanic activity. 
It is evident that this relation between the distribution of ores 
and the main lines of geological structure is of great importance 
both scientific and economical. Its discovery helps to correct an 
error ; for it has been believed that certain ores occurred exclu¬ 
sively in rocks of a certain age, whereas the truth is that certain 
physical conditions are required for their formation and deposition 
irrespective of the age of the rock in which they maybe deposited. 
It is also true that there is more probability of finding productive 
mines along the imperfectly explored portions of these great lines 
of disturbance than in any other part of the Pacific slope, and thus 
geology indicates the patli to be pursued in the development of 
the resources of the country. 
On the Pacific slope, as elsewhere, modern science and industrial 
interests arc indissolubly bound together and neither can safely 
dispense with the aid of the other. 
Sept. 3, 1886. 
