206 BOTANICAL GAZETTE [SEPTEMBER 
shifting sand hills, and has an altitude of 150 to 400 * (45-120). 
The area of the Colorado Desert has been estimated at 9,000 
square miles (14,40084*™),7 
The Mojave Desert lies on the north side of the San Bernar- 
dino Range, and its continuing spur, the Chuckawalla Mountains; 
eastward it stretches to the Colorado River, and northerly to 
and beyond our boundary lines. Its greatest length, east and 
west, measured in an air-line, from Gormans Station, at the head 
of Antelope Valley, to the Needles on the Colorado River, is 
about 130 miles (210*™). Its width, north and south, from the 
mountains which form its southern rim to our northern boundary, 
varies from 30 to 60 miles (48-96*™). No estimate of its area 
appears to have been made. Within our limits its altitude is 
much greater than that of the Colorado Desert, being 2,000 to 
3,500 * (660-1,067™), but beyond them it also sinks, in Death 
Valley, below sea level. 
Its whole surface is cut up by short isolated ranges and “lone 
mountains,’ which are surrounded by sloping mesas, or enclose 
basins whose lowest portions are occupied by ‘‘dry lakes.” Some 
of these are level expanses of hard, elastic clay, smooth and bare 
as a racetrack, and bordered by a narrow belt of nitrophilous 
vegetation. Receiving the scanty storm water that rolls down 
from the bare hills about them, they at times may be transformed 
into tenacious mud, or even be covered by a few inches of water. 
Or the floor of these basins may consist of what prospectors call 
‘‘self-rising soil,” a deep bed of loose alkaline powder, slightly 
crusted over, into which foot and wheel sink wearily; or, again, 
it may be covered with a snowy incrustation of soda salts. 
The highest mountain of the Mojave Desert is Ivawatch, 
6,290" (1,917™), on the northern boundary of San Beret 
dino county. Some twenty miles southwest is Pilot Knob, 5, 25° 
(1,684™), a noted landmark, as its name indicates. Mt. 
Manchester, near the Needles, is 4,570 * (1,448™) high. But 
the most important of these ranges are the Providence Mountains, 
7 This is for the part of it within the United States; beyond the boundary it con- 
tinues to the Colorado River and the head of the Gulf of California. Its width on the 
Colorado River is fully 75 miles (120*™), 
