cruickshank's practical planter. 



321 



and compounds in which iron forms a part), than ad- 

 vantage, from the dead vegetable matter not being 

 so much dissipated by aration and exposure to the 

 sun. We have often observed the effect of remain- 

 ing for a length of time in a state of considerable 

 dryness, dissipating the vegetable part of the soil, in 

 some of the old infield clays, where the crown of the 

 large ridges are raised up a foot or two above the ori- 

 ginal sm'face- level. At the crown of the ridge, the 

 vegetable clay mould often only extends down about 

 nine inches from the surface, the subsoil immediate- 

 ly under being nearly void of vegetable matter, and 

 extremely close tenacious clay, — a solid foot of it, 

 though of equal moistness, being nearly double the 

 weight of the same bulk of the vegetable clay mould 

 above it. From this clay, almost purely mineral, 

 being a little above the original surface-level, there 

 can be no doubt, that at one time it consisted of the 

 vegetable surface mould of the country, heaped up 

 by repeated ploughings, and that it has gradually 

 lost the vegetable part. The depth of vegetable soil, 

 near the furrows of the ridges, is generally found to 

 be greater than at the ridge crown. 



The same dissipation of vegetable matter takes 

 place when a ditch has been dug in clay ground, and 



X 



