. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. -irbnatAtmli*. /'// yw/ ErrECT OF PLANT AND ANIMAL LIFE 379 times to depths of many feet, bring about not merely a rear- rangement of soil particles through a transfer of materials from lower to higher levels, but also a condition of porosity whereby air and water gain access to the deeper lying portions, there to promote further chemical and physical changes. Naturally these insects limit their work to dry and light soils, where their operations may be compared with that of earth- worms whose operations are confined to moist
. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. -irbnatAtmli*. /'// yw/ ErrECT OF PLANT AND ANIMAL LIFE 379 times to depths of many feet, bring about not merely a rear- rangement of soil particles through a transfer of materials from lower to higher levels, but also a condition of porosity whereby air and water gain access to the deeper lying portions, there to promote further chemical and physical changes. Naturally these insects limit their work to dry and light soils, where their operations may be compared with that of earth- worms whose operations are confined to moist ones. Shaler has calculated^ that over a certain field in Cambridge (Massachu- setts) the ants have made an average transfer of soil matter from the depths to the surface sufficient to form a layer each year of at least a fifth of an inch over the entire four acres under observation. He further mentions a curious effect arising from the interfer- ence of the ants with the original conditions, in the separation of the finer from pig. 40.—Effects of ant-hills on soils, aa, the coarser particles. In sand accumulated in hill; l)h, material certain parts of New Eng- ^^^^^^ ^^^^ ^^^ «^^P^^' ^^^^^^^^ ^^^^ T T , T ., _ - vegetable mould, land where sandy sous had laid for a long time uncultivated, fields were covered to a depth of some inches with a layer of fine sand without pebbles larger than the head of a pin, while below the level of perhaps a foot the soil was mainly pebbles, with very little finer material. This condition, it is argued, was brought about by the tens of thou- sands of ants which each year, over every acre, in the process of building their dwelling brought up the finer material and deposited it in the form of a mound about the surface openings, leaving behind the coarser particles, too heavy for them to move. The common black and brown ants of the United States (Formica exsectoides) build upon the surface mounds in many cases from 1 to 2 feet in height, and 3
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectpetrolo, bookyear1913
