172 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
graben, bordered east and west by uplifted and well-dissected mountain 
blocks, Alvord valley may be highly commended. 
The Shoshone Range. — On returning from Oregon, I passed by the 
northern end of the Shoshone range in north central Nevada in an east- 
bound afternoon express train on the Central Pacific railroad between 
Argenta and Shoshone. My notes, rather hurriedly written at the time, 
are as follows: ‘A very fine fault block, with manifest recent and 
subrecent faulting. Broken fans; light-colored basal slopes, ripped 
with gullies ; uplifted grades, truncated spurs, revived streams in full- 
bodied spurs; spur tops dark gray, sides lighter; tops graded, sides 
ripped. Even fronted base, facing west and north; all excellent ex- 
amples for study. At some points on west base, very short fans, as if 
plain had been depressed.” 
This specimen of a block mountain interested me greatly. It served 
as an example for rapid review of many features that I had studied at 
more leisure in other ranges. It sufficed to show that physiographic 
evidence of block faulting may be easily and quickly recognized when 
it is looked for. It confirmed my opinion that such evidence compares 
well in logical and compulsory value with the stratigraphic evidence on 
which the demonstration of faulting is usually dependent. It strength- 
ened my belief in the importance and the possibility of describing all 
land forms rationally and systematically in view of their evolution. 
The description of the Shoshone range in the reports of the 40th 
Parallel Survey is so closely limited to matters of geological structure — 
as was natural enough at the time the Survey was made, and the re- 
ports were written — that no consideration is given to the physiographic 
features here discussed. The range is not mentioned in Gilbert’s or 
Russell’s reports, or in Spurr’s essay. The fuller meaning of my notes, 
supplemented by the maps and reports of the 40th Parallel Survey, and 
by the thoughts that accompanied the observations, is as follows : — 
The northern ten miles of the Shoshone range in north central Nevada 
is an east-dipping monocline of Weber quartzite overlaid by basalt (40th 
Par. Sury., map 4, west half). It is bordered on the north and west by 
the open alluvial plain through which Humboldt river wanders. From 
five to ten miles north of the range lies Shoshone mesa, composed of 
rhyolite covered by basalt, fronting southward in a strong escarpment, 
and dipping gently northward. The Central Pacific railroad skirts the 
base of the range for twelve miles along its northern end, giving a good 
view of part of its western outcropping face, and its northern cross sec- 
tion. The range has every appearance of being a dissected monoclinal 
