MANNER OF TRENCHING. 155 



to (c). The subsoil at (&) is then turned into the 

 trench (a), at the same time being finely broken 

 with the spade. The surface-soil at [d) is thrown 

 on the subsoil, spaded from [b) to (a), and so the 

 work is continued, — the surface-soil being always 

 in the same relative position as before. 



The reason for this course, rather than to turn 

 the surface-soil of (b) into the bottom of the trench 

 (a), and the subsoil above it, is readily found in the 

 fact, that when the tree is first planted its roots 

 reach but a few inches in depth into the soil, and 

 they require fine earth about them, which has 

 already been elaborated by the atmosphere and 

 fertilized by rain and cultivation. When the roots 

 find their way into the subsoil, it will have become 

 tempered, purified, and fertilized. There are soils 

 where the mixture of the two strata is, however, of 

 decided benefit. Such is the case when a stratum 

 of clay underlies a light soil, or the opposite. When 

 peaty land has a subsoil of clay, their mixture has 

 a remarkable eff"ect. The Farmers' Encyclopedia 

 says of such mixtures : 



" There is, perhaps, no agricultural improvement 

 in its immediate and permanent efi"ects more im- 

 portant than the careful and judicious mixture of 

 soils. This mode of improving the land was one 

 which very early engaged the attention of the 

 farmer. Nature herself, in fact, portrayed to him in 

 very intelligible language the means of producing 



