[ -87 ] 



Its retentive power is 82,25 5 hence I fliould judge it to be un- 

 fertile in this climate, unlefs fituatcd on a declivity wilh an unim- 

 peded fall ; it may be called a clayey loam. 



Mr. Young difcovered a remarkable circumftance attendant on 

 fertile foils ; he found that equal weights of different foils being 

 dried and reduced to powder, afforded quantities of air by dif- 

 tillation fomcwhat correfponding to the ratios of their values. 

 This air was a mixture of fixed and inflammable airs, both pro- 

 ceeding moft probably from the decompofition of water by the 

 coaly matter in the foil ; the diftillation fliould be made from a 

 retort glazed on the outfide— he found an ounce of dry foil, value 

 five fhillings - - produced - - ten ounce meafures, 



of from 5 to 12 produced 28 



12 — 20 42 



above 20 66 



This appears to be a good method of eftimating the proportion 

 of coaly matter' in foils that are in full heart, that is, not ex- 

 haufled, and freed from roots, &c. Another mark of the goodnefs 

 of a foil is the length of the roots of wheat growing in it, for 

 tHefe are in inverfe proportion to each other, as, if the land be 

 poor, the wheat will extend its roots to a great diftance in quefl 

 of food, whereas if it be rich they will not extend above five or 

 fix inches ; but of thcfe and fome other empyrical marks I fhall 

 fay no more, as they do not tell us the defeds of the foils. 



" «""»'"' A a t CHAP. 



