646 OREGON AND NORTHERN CALIFORNIA. 
and ten miles to the east commences the basaltic region, which is con- 
tinued up the Columbia. 
The eruptions of these basalts and lavas have taken place from 
fissures throughout the country,—fissures which were more numerous 
and extensive near the volcanic peaks, but also intersected the whole 
region to the coast. They cut through the tertiary rocks, and are also 
interstratified with them. At the Boundary Range, a sandstone con- 
taining fossils graduates into a volcanic tufa or conglomerate. 
The basalts are generally compact, without a granular or crystal- 
line texture, and they vary in colour from grayish-blue to black ; 
they are also cellular of all degrees and pass into a scoriaceous lava. 
Chrysolite in minute grains is usually present. At the Willammet 
Falls, both the cellular and compact varieties occur together, the same 
bed having the two characters in different parts, and in some places 
becoming scoriaceous. Along the Columbia below Vancouver, the 
rock is usually compact, with few cellules or none; and the same is 
the case with the variety near the grist-mill above Vancouver. On Inlk 
River, both the compact and cellular varieties occur together, and the 
latter passes into an amygdaloid containing nodules of stilbite, natro- 
lite, and chalcedony. At the Dalles, the basalt graduates into a lava 
of black and brownish-red colours. The rock of the Grand Rapids 
below Wallawalla, of the plains between Wallawalla and Colville, and 
of the country between the Columbia and Nisqually, is compact basalt 
and basaltic lava. On the Snake River, there are compact and cellular 
basalts and basaltic lava. 
These rocks, whether compact or cellular, are occasionally porphy- 
ritic, as is observed at Killimook Head, and in some parts of the 
Willammet district. Just north of the Elk Mountain, there isa grayish- 
green variety, which consists mostly of feldspar in semi-translucent 
crystals, with olive-green augite in grains. A mile to the southward, 
it becomes a dirty grayish feldspathic rock, consisting of opaque feld- 
spar in small imperfect crystals, and disseminated points of augite. 
Chalcedony and carbonate of lime are of frequent occurrence in 
some cellular varieties, changing them to an amygdaloid. Near the 
Clammat the chalcedony formed large plates in fissures, and also filled 
cavities. The chalcedony and agates which abound on the Willam- 
met and in other parts of the territory appear to come from the basaltic 
rocks. 
These rocks, whose different varieties we have been describing, 
