SECT. VI. MANURES. 81 



525 parts, exclusive of the roots of vegetable or to 

 about T ' T of its weight. 



Mr. Young observed that equal weights of differ- 

 ent soils, when dried and reduced to powder, yielded 

 by distillation quantities of air somewhat corre- 

 sponding to the ratio of their values. The air was a 

 mixture of fixed and inflammable airs, proceeding 

 probably from decomposition of the water ; but 

 partly, I should presume, from its capacity of ab- 

 stracting a portion of air from the atmosphere, which 

 the soil at least is capable of doing. 



The following is the analysis of a fertile soil, as 

 occurring in the neighbourhood of Bristol. In 400 

 grains, there were of 





Water 52 



Silicious sand - 240 



Vegetable fibre 5 



o 



extract 3 





Alumine 48 



Magnesia 2 



Oxide of iron 14 



Calcareous earth 30 



Loss ' 6 



Total. . . 400* 



But Mr. Kirwan has shown in his Geological Fertility 

 Essays, that the fertility of a soil depends in a great 



city 



* Agricultural Magazine, April, 1808. 



VOL. II. G 



r Of THE 



