73

Of value of from 5 to 12s. produced 2S ozs.

12—20 42

above 20 66

This appears to be a good method of estimat-ing the proportion of coaly matter in soils thatare in full heart; that is, not exhausted, andfreed from roots, &c. Another mark of thegoodness of a soil is the length of the roots ofwheat growing in it; for these are an inverseproportion to each other, as, if the land bepoor, the wheat will extend its roots to a greatdistance in quest of food; whereas, if it be rich,they will not extend above five or six inches;but of these and some other empyrical marks,I shall say no more, as they do not tell us thedefects of the soils.