294 The American Geologist. November, 1903. 
completely filled with sediments in the late Tertiary and Qua- 
ternary. Then followed the development of a lava plain of con- 
siderable extent, covering in fact the greater part of the area 
discussed in this paper. In spite of this volcani: interruption 
White river renewed its activity and cut its way though the 
flow and underlying rocks to a depth of nearly 2000 feet, only 
to be arrested again by a second eruption. Again, White river 
renewed its task and proceeded to incise itself in the second 
flow, cutting completely through the second filling to its former 
level. After the development of the valleys in the second lava 
sheet White river was interrupted in its course by local ejec- 
tions from near Green's point. These flows, however, were 
confined to the valley floors, extending down stream a distance 
of thirty miles. 
The present position of this stream with reference to the 
last flow is in part along the contact between it and the pre- 
existing slope or within the limits of the lava sheet itself. In 
places it has already succeeded in cutting through the entire 
thickness, while in others it has not yet accomplished that task. 
This case serves as an excellent illustration of laking in 
consequence of faulting, and subsequent development of drain- 
age which is in part inverted and in part diverted. 
Springs. 
The springs of the region may be divided into the follow- 
ing groups : the extinct springs, the common springs, the hot 
springs, and the salt springs. 
The Extinct Springs. — These springs are now represented 
by the Elsesa and Little Cibicu travertine deposits. As they 
have been described under the "Post Glacial," they need not be 
furl her mentioned here. 
The Common Springs. — All the streams of the region head 
in springs and are fed by springs gushing from the canyon 
walls in their channels. Were it not for these springs the water 
courses would be dry most of the year. Besides those in the 
canyons, others occur on the mesas and in the mountain dis- 
tricts, and although they are small and not numerous they are 
quite an aid to stockmen in furnishing water for the stock of 
the country. 
It has been noticed for several years that the springs south 
of the Mogollon range are gradually drying up; and it is pre- 
