Concentration by WcatJicring— Kiinbull. 157 
ering escarpments rising from the river canon. On the op- 
posite side foothills of the same range fall ofif toward the val- 
ley of the Columbia. 
At the time of my visit to the region, in the month of Sep- 
tember, 1890, some eighteen contiguous mining claims had been 
located, together forming a loop, and covering the bottom lands 
and both mountain sides. The whole stretch of locations 
compassed what was concluded to be remnants of a faulted 
l)oss or dome of a stratiform ferriferous series. By subsidence 
of the arch the medial portion overspreads the narrow vallev 
bottom wherever not obliterated by erosion. Uneroded parts 
in minor undulations traverse low hillocks. Hence gentle 
quaquaversal dips and small saucer-like basins. Steep re- 
treating dips of the same series enter the mountains on either 
side beyond the planes of fault at dififerent elevations, namely, 
at 4,675 feet on the east and about 1,000 feet lower on the 
opposite side. From the greater part of the area of the bot- 
tom lands the ferriferous beds have been eroded. Even on the 
circling line of mineral locations corresponding to an outer 
margin of the subsided arch their preservation is only partial. 
The present river channel follows the line of the western fault. 
Affected as they are by unequal erosion and somewhat 
variable in section, the beds in question present a total thick- 
ness of from six to eighteen feet. They constitute three divis- 
ions of an amorphous aggregate. This series is underlain b\ 
crystalline pyroxene and surmounted by micaceous sandstone 
passing into conglomerate, both conformable and of meta- 
morphic type. 
The notable occurrence of iron ore, properly so discrim- 
inated, is at the base of the series of ferriferous, or, rather, 
ferruginous, beds. In quality and thickness this is far from 
uniform. Its development is confined to wet places and ex- 
posed ledges. 
In circumstances thus favorable to atmospheric oxidation 
and percolation of water, magnetite, martite, hematite and 
limonite have been exfoliated as an insoluble residuum from 
decomposition of the basic aggregate. These mixed products 
have a foliated structure. The separate folia serve to dis- 
tinguish progressive exfoliation of iron oxide. Thus siliceous 
residuums separate lustrous folia of chromiferous magnetite, 
