153 



water could by this means be brought within reach of the 

 smaller plants when the level of the ground-water is twenty 

 feet or more below the surface, as it is in Mason county. 



The water-retaining properties of the sand are also of im- 

 portance to the vegetation. The effect of the percolation of 

 rain water is the saturation of the upper layers of sand to a 

 depth dependent upon the amount of rain. If the surface is 

 dry or only partially saturated, that will hrst be brought to full 

 saturation, and the surplus water will sink down to lower 

 levels. None is removed by surface drainage, so that, aside 

 from the small quantity remaining attached to plants and other 

 objects, all the rainfall sinks at once into the sand. Evapora- 

 tion from the surface removes large quantities of water, but ac- 

 cording to results obtained by King ('04, p. 159) in North Caro- 

 lina this is less from sand than from loams or clays. By the 

 drying out of the upper few inches a mulch of loose sand is 

 formed, which still further reduces evaporation. King found 

 that eight ninths of the water which might be expected to 

 evaporate is thus retained, and that during twenty-eight days 

 in July and August, 1902, only .205 in. evaporated from the sur- 

 face. The climate of central Illinois during the summer is not 

 so different from that of North Carolina as to lead us to expect 

 here any considerable variation from the al)Ove record. The 

 moisture in the deeper layers of sand is thus effectually con- 

 served. After a considerable period of drought, as in August,* 

 1894, when only .21 in. of rain had fallen in eighteen days, 

 the sand at a depth of three inches was still moist enough 

 to compact readily in the lingers. Thus, while the actual 

 amount of water present is small, it is neverthele.ss constant, 

 and it is a common statement of the farmers in Mason coun- 

 ty that corn grown upon the sand is less susceptible to 

 drought than that on the more fertile fields of loam. Accord- 

 ing to Professor J. G. Mosier, of the Illinois Agricultural Ex- 

 periment Station, the "firing" of corn on the sand is due to a 

 deficiency of plant food and not to lack of water. Some inter- 

 esting cases of other soil types, having similar but more marked 

 powers of water conservation, are reported l)y Whitney ('98). 



