SOILS. 33 



2d. That there would seem to be an in- 

 comprehensible good or ill .in some soils, 

 and which is either food or poison, ultimate- 

 ly, to plants deposited in them 1 *. 



3d. That prudence should therefore di- 

 rect putting different plants into the same 

 soil, to the intent that each may search out 

 that good, or discover that ill: and after- 

 wards, the removal of the poisoned, and 

 careful retention of the healthy and w r ell- 

 fed plants. 



4>th. As the best criterion, in a doubtful 

 case, of the quality of soil fitted for forest 

 timber, it might be advisable to plant many 

 kinds, encouraging those which seem to 

 thrive best, and which would become the 

 most valuable trees, by thinning away the 

 others as they advance. For, a healthy tree, 

 although of less intrinsic value as timber, is 

 preferable to that in a languishing state, 

 whose wood, were it healthy, might be much 

 superior; besides, in point of gratification to 

 the beholder, there is no comparison. 



* " It is well known, that where mines of iron, lead, 

 or copper, lie near the surface, no plant will thrive in 

 perfection ; as is the case on the LeadhilJs in Scotland." 



