198 THE LUKE OF THE LAND 



level in Arizona, and even below the sea-level in south- 

 ern California, up to an elevation of at least 6,000 or 

 8,000 feet, along the eastern border of the Bocky Moun- 

 tains, and in the elevated valleys of New Mexico, Colo- 

 rado, and Wyoming. It occupies depressions of all 

 sizes up to valleys having an area of hundreds of square 

 miles. Although occurring throughout the arid re- 

 gion, it can be studied to best advantage in the drain- 

 less and lakeless basins in Nevada, Utah, and Arizona. 



PEAT SOILS. 



The heavy soils whose origin has been described are 

 essentially of a mineral nature. The quantity of or- 

 ganic matter in such soils may vary from a mere trace 

 to a few per cent, but they never lose their mineral 

 characteristics. When a soil on the other hand is com- 

 posed almost exclusively of vegetable mold it belongs 

 to quite another type. Such soils are called tule, peat 

 or muck. In this country there are thousands of acres 

 of peat or muck soils; the largest contiguous deposits 

 being found in southern Florida. The origin of these 

 soils is easily understood. Whenever rank vegetation 

 grows in such a location as to secure for the organic 

 matter formed a slow decay, there is a tendency to the 

 accumulation of vegetable mold in shallow water or on 

 marshy ground and where other conditions are favor- 

 able to such accumulations. In Florida the peaty soils 

 have been accumulated about the margins of lakes. 

 During the rainy season the marshes bordering these 

 are partly covered with water, but the vegetation is 

 very luxuriant. The water protects the vegetable mat- 

 ter from being destroyed by fire. It therefore accumu- 

 lates from year to year and is gradually compacted into 

 quite a uniform mass of vegetable mold. 



