Forest physiography; physiography of the United States and principles of soils in relation to forestry . washes have a most variable supply as regards both quantity andquality. The lakes are due to the damming of the watercourses bylava flows. Some of them have become dry by the cutting down oftheir outlets and the accumulation of sediments; their floors are nowgrass-covered and picturesque glades. The soils of the San Francisco volcanic field vary from adobesoils of the floors of temporary lakes and ponds to the pervious cinder COLORADO PLATEAUS 295 and scoriaceous soils of the slopes of volc
Forest physiography; physiography of the United States and principles of soils in relation to forestry . washes have a most variable supply as regards both quantity andquality. The lakes are due to the damming of the watercourses bylava flows. Some of them have become dry by the cutting down oftheir outlets and the accumulation of sediments; their floors are nowgrass-covered and picturesque glades. The soils of the San Francisco volcanic field vary from adobesoils of the floors of temporary lakes and ponds to the pervious cinder COLORADO PLATEAUS 295 and scoriaceous soils of the slopes of volcanic cones and ridges. Be-tween these two extremes are gravelly loams of several varieties moder-ately pervious to water and best adapted of all the soils to the growthof forests. The coarse cinder soils lose water so rapidly that they areextremely sterile, while the adobe soils crack open when dry and swellwhen wet and are not adapted to forest requirements.^ The San Francisco Mountains are encircled by barren plateau country,but they are themselves covered with a beautiful forest of juniper, pine,.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
