12 THE PRACTICE OF THE 



phnts, fo many tons every year, that the 

 richeft land would be foon exhaufted of all its 

 fine parts, and, if carried away by the crops, 

 could never be recruited again, but the land 

 would be exhaufted of all its fertile parts, 

 and would remain for ever after emaciated 

 and totally barren ; which is contrary to ex- 

 perience ; for the lands that were noted for 

 their fertility and depth one or two centuries 

 ago are known to continue the fame to this 

 day; they have ftill the fame depth of ftaple, 

 and the lame remarkable fertility, that they 

 had in former times ; whereas, had every crop 

 for a feries of ages, or only for one or two 

 centuries, carried off part of their fertile 

 earth, they muft long ago have been totally 

 exhaufted of their fertility. We muft there- 

 fore endeavour to dilcover elfewhere the ge- 

 nuine fource of the vegetable nomimtnent, by 

 which fuch weighty crops are obtained every 

 year, without diminimmg the fo 1. 



The earth is {"unrounded by a fluid body, 

 commonly called the air, but more properly 

 the atmofphere, which confifts of all kinds of 

 matter, of air, water, lalts, oil, fire, and 

 earths of every kind ; for all the volatile 

 parts that arife from the fea, from lakes; 

 -rivers, and other waters, or moift places ; all 

 the exhalations from the earth, from hills, 

 vallies, caverns, < mines, or other dry places 

 that are lighter than air, afcend into it, float, 

 and mix there : the perforation likewife from 



trees 



