Page:Isaiah Bowman - Desert Trails of Atacama (1924).pdf/72



Deserts are no more alike than mountains or plains. In some there is a marked degree of rainfall, say ten or twelve inches a year, in others less than one inch a year; and of course there is a corresponding difference in the amount of vegetation. It was of an area near Tocopilla that the naturalist Ball wrote, “1 found what I had often heard of, but in whose existence I had almost ceased to believe—a land absolutely without a trace of vegetable life.”

While Philippi found the seaward slopes about Paposo at elevations of 500-1800 feet enriched with vegetation during nine months of the year, in the interior he passed two vegeta- tionless stretches of 10 or 25 leagues respectively. I have already spoken of the vegetationless character of the country eastward of Central Lagunas. Similarly riding to Quillagua southward of Central Lagunas in June, 1907, not a single spear of grass, not a single shrub or tree, not even a cactus did I see over a distance of 40 miles. The trail passed over sand and gravel, in and out of dry ravine beds, over thick salt deposits with rough buckled surfaces, and occasionally over a ledge of rock or a flow of lava. Nowhere was there any vegetation in sight. It was a thoroughly naked land. But these are exceptional conditions. As a rule at least a little vegetation is to be found along seepage lines in the ravines or desert hollows, where slow-moving ground water makes its exit. The plants of the desert are scattered in clumps and lines here and there in sympathy with the ground water or the surface drainage, and sometimes there are wide stretches of bush-covered country that depend upon natural subirriga- tion of the soil, as in the Coquimbo valley at the southern end of the Desert of Atacama, and in the Pampa del Tamarugal