REVIEWS AND BOOK NOTICES. 857 
of hot springs. Upon all this, in some localities, continuing up to 
the time of the drainage of this lake, were deposited the mod 
volcanic clays, sands, sandstones, and pudding-stones, which 
reach an aggregate thickness of 800 to 1,000 feet. Above the 
transition from the hard basalt to the more yielding breccia, so 
that the river easily carved out a channel through it ; the vertical 
walls are clearly seen from below the falls, passing diagonally 
across the rim. The Lower Falls are formed in the same way ; the 
entire mass of the water falls into a circular basin, which has been 
worn inte the hard rock, so that the rebound is one of the mag- 
nificent features of the scene. Below the Lower Falls the sides of 
can w th 
Where the river has cut its channel through the hard basalt, 
the irregular fissures, which undoubtedly extend down, in some 
manner, toward the heated interior, are distinctly seen. Local 
deposits of silica, as white as snow, sometimes 400 or 500 feet in 
thickness, are seen on both sides of the Yellowstone. These also 
are worn into columns, which stand out boldly from the nearly 
_ The Yellowstone lake is described in glowing terms. It is 22 
miles long from north to south, averaging 10 or 15 miles in width 
from east to west, with a depth of 300 feet. “It is fed by the 
snows that fall upon the lofty ranges of mountains that surround 
