228 SELECTIONS FROM ADDRESSES. 



nure for the upper, and pits are dug to a considerable depth 

 where there is any prospect of obtaining it. 



T had occasion, during my residence in Scotland, to examine a 

 number of slates from a certain district in Wigtonshire, with 

 reference to their per-centage of lime. The difference was found 

 even greater than had been anticipated, some of them contain- 

 ing six or seven per cent., and others little more than a mere 

 trace. These layers were a part of one continuous series, and 

 each formed soils in a comparatively small district. These soils 

 of course varied as did the slates, in their proportion of lime. 

 The layers of slate were thin, and hence it might happen that 

 there were two or three kinds of soil on the same farm. The 

 farmer would find then, that the application of lime on one field 

 was beneficial, on another quite useless. He would puzzle him- 

 self to make out the cause, when the simple reason would be 

 that one soil had enough lime already, but the other had none 

 at all. In this way may the greater part of the contradictory 

 views regarding lime be reconciled. 



Quite as great differences as the above are to be found in soils 

 derived from sandstones. There are various formations of sand- 

 stone as of limestone, and they also differ greatly in their com- 

 position ; producing, in some cases, miserable shifting sands, and 

 in others some of the richest soils known. 



The same variation is frequently found among the granite 

 rocks, as I will exemplify by the following table. 



This table is intended to show the general composition of 

 certain common minerals and rocks. The names may not be 

 understood by many, but that is of no consequence to my pres- 

 ent purpose. It is enough to know that they are names of com- 

 mon substances and rocks, some of which are met with in 

 almost every neighborhood : — 



