SOLUBLE SALTS AND STRUCTURE 117 



by the following table. The force required for a uniform 

 depth of penetration of the knife-edge is reduced to the 

 basis of 100 for the check. 



1. Check 100.0 



2. Calcium carbonate, 5 per cent 98.5 



3. Calcium oxid equivalent to CaO in 2 56.5 



4. Calcium carbonate, 10 per cent 111.0 



5. Calcium oxid equivalent to CaO in 4 ... . 43.5 



6. Calcium carbonate, 25 per cent 95.0 



7. Calcium oxid equivalent to CaO in 6 33.6 



This table indicates that the oxide of lime, or the 

 hydrate as it would be in the wet soil, is more efficient 

 in granulating the soil than is the carbonate. It is pos- 

 sible that this difference is the result of the short time 

 of contact of the lime with the soil, which was only 

 a few weeks. In the soil the hydrate will in time change 

 to the carbonate, owing to the presence of carbon 

 dioxicl in the soil, so that in the end the form of the 

 lime would be the same. These figures emphasize 

 a fact recognized in practice, viz., that a considerable 

 time is necessary for lime to have its full effect on the 

 soil, and therefore it should be applied some months 

 or even a season or two in advance of the crop it is to 

 benefit. 



Warington reports the statement of an English 

 farmer to the effect that by the use of large amounts 

 of lime on their heavy clay soil they were enabled to 

 plow with two horses instead of three. It is generally 

 true that soils rich in lime are well granulated, and 

 maintain a much better physical condition than soils 

 of the same texture which are poor in lime. 



