No. 4.] 



KEEPING UP FERTILITY. 



77 



physical condition of the soil. Still, I shall be obliged to 

 confine my attention for the most part to a consideration of 

 the use of these materials in their relations to the composition 

 of soils and crops ; or, in other words, I shall consider the 

 sul)ject chiefly in its chemical and not in its physical rela- 

 tions. 



Before entering upon the discussion of this part of my 

 subject, I desire to ilhistrate, by calling attention to the 

 results of the physical analyses of a few soils, the intimate 

 relation of physical conditions to fertility. The method of 

 analysis followed in obtaining these results, for which I am 

 indebted to Prof. Chas. Wellington, is that proposed by 

 Prof. E. W. Hilgard of California. The object aimed at is 

 to separate the soil into a number of diiferent grades, accord- 

 ing to fineness, and in accomplishing this result water is 

 used. According to Hilgard's system, the soil from which 

 all stones and pebbles are first removed is divided into thir- 

 teen different grades, respectively denominated coarse, and 

 fine grits ; coarse, medium, fine and finest sands ; dust ; 

 coarsest, coarse, medium, fine and finest silt ; and clay. 



The soils selected for this illustration are the Agawani 

 "plain" land, which is of a very low grade of fertility, 

 and on which crops sufier very seriously in dry weather ; the 

 soil of the Hatch Experiment Station grounds at Amherst, 

 which is fertile and of nearly ideal phj'sical character ; and 

 the soil of the diked salt marsh of Marshfield, which is heavy, 

 and becomes wet and sodden in wet seasons, and bakes and 

 cracks during drought. 



