1238. The mechanical action of irrigation is, that it softens the soil and preserves the roots of plants in a healthy state. It also serves to dissolve the various earthy matters contained in the soil, and acts as a medium by which they are taken up into the plants. 'Very dry parched land,' observes Professor Solly, 'is, of course, improved by irrigation, when from the heat of the climate the greater part of the natural moisture of the soil is evaporated. Under such circumstances, the artificial application of water is necessary for the successful cultivation of plants, and accordingly it is a constant part of the agriculture of tropical countries, in the cultivation of rice and similar crops.' (Solly's Rural Chemistry, 2nd edit., p. 196.)
