46 CLIMATE AND RESOURCES OF 



were, become endowed with life, and acts as a breathing 

 object, inhaling heat by day, exhaling it by night; abstracting 

 from the air carbonic acid gas and ammonia, and both giving 

 to and taking from it water. 



The system of deep cultivation of the soil, and thus allowing 

 the water to sink into it too deeply to be lost by evaporation, 

 is that which, according to Marsh, was recommended by 

 Palissy and Babinet for the formation of artificial springs. 

 In the case of deep cultivation generally over a country, more 

 especially a level country, there is a reservoir of water under 

 every field, sufficient to supply the wants of vegetation held 

 there by the soil itself. We enlist in our favour the powers 

 of capillarity possessed by the soil. In what is the action of 

 loosened soil different from that of forests in retaining 

 moisture ? 



The upper loosened soil acts as trees do, and shades the 

 soil below it. The loosened soil acts as a sponge, as the 

 leaves of trees on the surface-soil of a forest do, and arrests 

 the rain falling on it, and gives it time to sink under cover, 

 and when the rain falling on the surface has sunk through 

 the upper loosened soil it is as effectually protected from the 

 evaporative influences of sun and wind as is water in the soil 

 of a forest. The fact that leaves lying on the ground prevent 

 evaporation of moisture from it, has led gardeners to employ 

 leaves, straw, and other refuse vegetable matters to spread on 

 the surface to keep the ground moist by preventing evapora- 

 tion. This is called a mulch. Now, soil of every description, 

 loosely spread on the surface, acts in the same way ; but 

 different soils do nob act equally, and their powers of prevent- 

 ing loss of moisture by evaporation appear to be in inverse 

 ratio to their powers of retaining heat. So humus, or decayed 

 vegetable matter, which is placed at the bottom of Schubler's 

 list of earths, would have the greatest power of preventing 



