404 
TURNER. 
rect, his explanation of the formation of the basin ranges by 
gravitative settling finds confirmation in a paper by William 
Hopkins, in 1842 (VII), who demonstrated that a series of 
wedge-shaped blocks, formed by a system of normal faults 
cutting a given area of crust resting on a molten magma, 
would be differentially displaced, and that the blocks with 
the base of the wedge downward would be elevated relatively, 
and those with the apex of the wedge downward would 
settle. The relatively elevated blocks would form a system 
of flat-topped ridges with steep sides, the intervening blocks 
forming the floor of valleys. 
This would not, however, account for the monoclinal 
ridges, which Professor Le Conte supposes to have been 
rhomboidal blocks, the overhanging side of which would 
tip, heaving up the other side. 
It will be seen from Le Conte’s earlier writings that he 
considered the Sierra to have attained nearly its present 
elevation at the time of its upheaval, and that at about that 
time a fault was formed west of Owen’s Lake, which ran into 
a fold at about Lake Mono; also that the elevation of the 
range at the close of the Tertiary was a very slight affair. 
He now evidently considers the range to have attained its 
present elevation by a considerable elevation at the close of 
the Tertiary, with the formation of a line of normal faulting 
along the base of the steep eastern scarp of the range. 
We will here assume Mr. Diller’s extension of this line of 
faulting through Mohawk and American Valleys to be cor¬ 
rect. It will follow that the amount of faulting in recent 
times has not been great. Since the highest lake deposits 
occur on both sides of the line of fracture at an approximate 
elevation of 5,000 feet, it is evident that the amount of fault¬ 
ing since the existence of the highest stage of the lake must 
be measured in tens and not hundreds of feet. 
On the supposition that the Pliocene beds containing the 
fossil leaves and the Mohawk Post Office beds are approxi¬ 
mately of the same strata, these also being on opposite sides 
of the line of fracture and nearly of the same elevation, the 
