54 THE PRINCIPLES OF 



But whatever the cause, there is much less chalking done 

 than there used to be in the old days. A chalk sub-soil 

 is also cool and moist, so that in a long and protracted 

 drought it is pleasant to notice how the thin white soils of 

 the upper chalk retain their verdure. 



We must therefore take the sub-soil into account as not 

 only a condition of fertility, but likewise, as it is evident to 

 the eye, an indication of fertility. 



Another indication of fertility or barrenness is geological 

 position. Agricultural teachers ought to have some insight 

 into the subject of geology. It might be considered feasible in 

 speaking of the distribution of soils in this country to describe 

 them county by county, and to take the geographical rather 

 than the geological view of the distribution of soils. If we 

 take up the Journals of the Royal Agricultural Society, we 

 will find that the agriculture of every county in England 

 has been described. The reading is exceedingly instructive, 

 whether we take up our own particular county in order to 

 better understand it, or take up the subject for the purpose of 

 comparison. The agriculture of Wiltshire, the agriculture of 

 Oxfordshire, or the agriculture of Northumberland or Lanca- 

 shire, form very valuable reading. But in all cases the 

 authors, in describing the different soils of their counties, are 

 obliged to resort to a geological classification. 



Again, we must remember that knowledge is much more 

 easily retained, and much more easily communicated if it 

 is connected. When facts come to be strung together like 

 beads upon a necklace, that is to say, when there is one 

 thread running through a large number of isolated facts, it 

 is much easier to carry those facts away with us. It is with 

 that object chiefly as connecting various -agricultural facts 

 that I introduce geology. It so happens that England 

 can be readily divided and described, by observing the 

 succession of the various geological strata, as the soils of 



