cruickshank's practical planter. 325 



houses, though applied in no larger quantity than is 

 usually given of farm-yard manure, and though the 

 clay appear quite free from vegetable matter. It is 

 improbable that the resting of the clay from produc- 

 tion could have any effect to occasion this fertility, 

 ^Ve considered it to arise chiefly from a quantity of 

 nitre ha^dng been formed in, or deposited about, the 

 walls from their long proximity to animal effluvia 

 and to atmospheric air. The fertilizing effect of the 

 dike system of summer-fallow, and even of the pre- 

 sent system, may also depend in part on the forma- 

 tion of nitre, well known to be a powerful manure or 

 stimulant in this country. In dry seasons we have 

 scraped together handfuls of salts, partly nitre, from 

 the exposed surface of clay-banks. Should a consi- 

 derable part of the fertilizing effect of fallowing arise 

 from the formation of nitre, the application of lime 

 and putrescent manures to fallows, in the early part 

 of summer, will be advantageous, as the presence of 

 both are favoiu-able to the formation of nitre. Of 

 course, the utility of encouraging the formation * of 



* There is a deposition from the atmosphere of saline matter 

 going on at the surface of the earth, either evaporated from the 

 ocean, and falling with the rain and dews, or formed hy gaseous 

 combinations — most probably both. la countries where the quan- 

 tity of rain is insufficient to wash this saline accumulation away 

 into the ocean as fast as it is formed, it increases to such a degree 



