194 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



But the soil is not governed solely by the conditions that happen 

 to obtain at the time being ; it is profoundly influenced by those that 

 have passed ; indeed, one might go so far as to say that its properties 

 are determined largely by its history. The shape, the size, and to a 

 large extent the composition of the mineral particles are the result of 

 forces that caused the fragments of rock to chip off long ages ago, and 



N as nitrate 



laches Rainfall per 10 fi gr. dry soil 



have governed their wanderings ever since. The nature of the organic 

 matter depends on the past vegetation, and this in turn on the climate ; 

 the micro-organic population is determined by vegetation, climate, 

 and other causes. The soil as we see it to-day is the result of changes 

 and climates long since past as well as of those now present. In short, 

 the soil is the embodiment of its past history, and can only be studied 

 properly in the light of its history. 



