OF SOIL AND MAJfDBE. 335 



as plastic clay itself. It is by obtaining a mean be- 

 tween these two extreme cases that tha soil is formed 

 most favourable to the growth of plants in general ; 

 hence the mixtures of peat, loam, and sand, which 

 are so continually employed. These substances 

 counteract each other's influences, the loam by conso- 

 lidating the sand, and the sand by lightening the 

 loam, and the peat by binding them all together, and 

 preserving their perfect admixture, independently of 

 its manuring qualities. It is, however, a well ascer- 

 tained fact, that loam containing a considerable quan- 

 tity of calcareous matter is in general much better 

 suited to cultivation than such as is destitute of it : 

 the reason for which seems to be, in part, that calcare- 

 ous earth enters largely into the organisation of all 

 plants, in which it is deposited in the state of the 

 oxalate and phosphate of lime ; and, in part, because, 

 as was shown by Davy, there is a strong action be- 

 tween the lime and vegetable matter contained in 

 soils, the result of which is a compost partly soluble 

 in water.* 



* [The extensive beds of marl distributed over » considerable 

 portion of this country are just coming into use, and will ultimately 

 prove valuable in the highest degree to the cultivator. We have 

 found this substance peculiarly adapted to promote the growth and 

 productiveness of the Peach and the Vine. In New Jersey, thou- 

 sands of acres of sandy soil formerly sterUe and worthless have been 

 rendered fertile and productive by the application of marl. In other 

 districts it is now used to a considerable extent for top-dressing 

 grass-land, corn fields, ifec From ten to forty loads per acre, ac- 

 cording to the quantity of calcareous matter contained, are generally 

 applied. A. J. D.] 



[It ia easy to understand the rationale of the favourable effect* 



