538 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



ing, the roller is applied immediately after the seed is put in. 

 AY hat is accomplished by this is, that the seed is pressed tight- 

 er in the soil and brought into better contact with the soil- 

 moisture; but, at the same time, more moisture is brought to 

 the seed by the rolling, since the compacted soil-layer draws 

 more water from below. That is, water is not retained in 

 the soil by rolling, but it is brought just where it is most 

 wanted namely, near the seed. Further, the roller is often 

 used after the seed is up and the plants have attained a cer- 

 tain height. Although here an advantage, perhaps, likewise 

 comes from bringing up water from lower layers to the 

 roots that are still too short to reach it, and to the just-form- 

 ing root-branches, yet the main use is to press the young 

 plant tightly in the soil and give it a firm hold there." 



"Hoeing helps to hold the moisture in the soil; the looser 

 the surface of the field is kept, the more moisture will the 

 soil retain. We shall always hoe when the surface is crusted ; 

 for, aside from the other disadvantages the crust brings, it 

 has the same ill-effect as rolling it abstracts moisture from 

 the soil." 



Experiments on Evaporation of Water from the Soil. 



In the report of the Connecticut Experiment Station for 

 1877, Professor S. W. Johnson describes some experiments 

 undertaken to obtain more light upon this subject. . Clayey 

 loam, peat, and emery were placed in cylinders, kept con- 

 stantly supplied with water at a uniform level below, and 

 weighed daily to determine loss by evaporation. Iu general, 

 the evaporation from the surface increased with the fineness 

 of the particles. There seems to be a degree of fineness, how- 

 ever, at which evaporation attains its maximum, and beyond 

 which it decreases again. These results, like those obtained 

 by Nessler, Wagner, and Schleh, lead to the inference that 

 evaporation is more rapid from compact than from loose soils. 



PHYSICAL PROPERTIES OF CLAY SOILS. 



The Properties of Clay. 



Professor Johnson has also called attention to the proper- 

 ties of clay as shown by the investigations of Schloessing, Ilil- 

 gard, and other experimenters, and late observations by him- 



