Review of Recent Geological Literature. 133 
another quarter was tributary to the companion, lake Lahontan, de- 
scribed in a previous monograph by Russell ; and the remaining half of 
this arid region of interior drainage held some twenty-five smaller lakes, 
much exceeding, however, the saline lakes and playas to which they are 
now reduced. 
Foremost among the conditions producing the arid climate of the 
Great Basin and of the peninsula of Lower California, as pointed out 
by Dutton, is the branch of the Kuro Siwa current which sweeps south- 
ward with a width of about 300 miles along our Pacific coast. At the 
north this current is warmer than the adjoining part of the ocean, and 
the warm winds blowing from it over Alaska, British Columbia, Wash- 
ington, and western Oregon, are cooled by the land and precipitate their 
abundant moisture in copious rains; but as this current continues to 
lower latitudes it slowly loses its heat and on the coast of California is 
cooler than the oceanic area farther west, so that the winds crossing it 
are cooled and depleted of much of their moisture before reaching the 
land. In these latitudes, moreover, the heated land area during the 
greater part of the year condenses little or no rain from these winds, ex- 
cepting on the high mountain ranges. Plentiful rains and snows fall on 
the lofty Sierra Nevada, extending 400 miles along the west side of the 
Great Basin, into which the air currents then descend, thirsty for 
evaporation. 
But the shore-lines and lacustrine beds of lake Bonneville, like those 
of lake Lahontan, demonstrate that twice the Pleistocene climate of this 
region became more humid, though to less degree than the present 
climate of the eastern half of the United States. The humid epochs 
were divided by a long interval of aridity, in which, as Mr. Gilbert lias 
shown, lake Bonneville was perhaps wholly evaporated, its soluble 
mineral matter becoming intermingled and covered with playa silts, so 
that it could not be redissolved by the water of the lake during its 
second rise, which may have been nearly fresh. The first great rise of 
lake Bonneville, lifting its level to within 90 feet of the lowest point of 
the enclosing water-shed, is recorded by numerous beaches, marking the 
oscillations of the lake level under the varying influence of secular 
climatic changes, and by a thick lacustrine deposit of yellow clay. A 
long interlacustrine epoch is known by overlying alluvial gravel and 
sand. The second rise of the lake reached the level of overflow, ap- 
parently after the water surface had been long held within five to twenty 
feet below that level, forming a widely spread deposit of white marl, 
and the well defined highest beach ridges and eroded cliffs, which Gil- 
bert names the Bonneville shore-line. The time required for the great 
amount of wave-work at this level would be made possible by long con- 
tinued underground drainage from the lake through the alluvial de] 
of Cache Valley, over which a slightly higher rise of the lake finally gained 
asuperficial outflow to the Columbia river, and then rapidly cut a channel 
375 feet deep in the alluvium to a sill of limestone. At this lower level, 
marked by the Provo shore-line ami deltas, the lake was held for a long 
