a PROCEEDINGS OF THE NATIONAL MUSEUM.: VOL. 62. 
exposed in many places in street and railway cuttings and it is from 
these exposures that the minerals described below have come. At 
Division Street and Mallon Avenue, which are shown in the photo- 
graphs reproduced as Plate 1, two distinct flows of basalt are exposed. 
At the point marked (x) at the right of the lower picture there was 
found between the flows a portion of a tree trunk 10 feet (3 meters) 
in diameter and 5 feet (1.5 meters) long, charred at one end. Dr. 
Frank H. Knowlton identified this wood as belonging to the genus 
Sequoia but of undeterminable species. The wood is dark, hard, and 
somewhat brittle, resembling ebony more than redwood, but it is so 
well preserved that the log was sawed into boards which were made 
into a box. Although some coaly material may be seen in the pores, 
the wood is not conspicuously lignitized. Spokane is practically at 
the eastern limit of the basalt area and the lava here is relatively 
thin, and hills of older rocks project through it in places. The very 
fluid material filled the floor of Spokane Valley extending up to 
Coeur d’ Alene Lake and for many miles up the tributary Coeur d’ Alene 
and St. Joe Valleys, giving these tortuous canyons a level floor of solid 
stone. This has been cut through by later erosion, and the basalt 
remains as flat topped terraces along the valley sides. 
Mr. Fair reports that certain wells sunk in the city of Spokane 
have penetrated 264 feet (SO meters) of basalt and 286 feet (87 
meters) of silt and have been drilling for 500 feet (152 meters) in 
eranite in search of oil. The silt which underlies the basalt is 
apparently a lake deposit formed in water ponded by damming of 
the Spokane Valley by earlier flows of the lava and covered by the 
later flows. It has been found to contain abundant plant remains 
which are of Upper Miocene age. 
The rock of the flows in Spokane varies from spongy material, in 
which half the volume is occupied by irregular open cavities, to dense 
compact granular basalt which shows typical columnar structure. 
In places the material from surfaces of flows is glassy, forming a 
basaltic obsidian, and there are occasionally inclusions of mud. 
PETROGRAPHY OF THE BASALTIC ROCKS. 
The specimens of Spokane basalts submitted to the writer for 
examination are varied in appearance, but those which enclose the 
vesicles containing minerals are all of two major varieties character- 
ized as light and dark basalt by Mr. Fair. Both of these are 
equigranular moderately fine-grained holocrystalline rocks. The 
light-colored variety is light gray in color and granular in structure 
with a harsh lusterless surface on fresh fracture. It is perfectly 
fresh with no sign of alteration. As contrasted with this the 
dark-colored variety has a dark greenish brown color, greasy luster, 
and dense conchoidal fracture. In thin section under the micro- 
