C 16 3 



to be discovered with regard to the best methods 

 of rendering animal and vegetable substances soluble ; 

 with respect to the processes of decomposition, how 

 they may be accelerated or retarded, and the means 

 of producing the greatest effects from the materials 

 employed : these subjects will be attended to in the 

 Lecture on Manures. 



Plants are found by analysis to consist princi- 

 pally of charcoal and aeriform matter. They give 

 out by distillation volatile compounds, the elements 

 of which are pure air, inflammable air, coally matter, 

 and azote, or that elastic substance which forms a 

 great part of the atmosphere, and which is incapable 

 of supporting combustion. These elements they gain 

 either by their leaves from the air, or by their roots 

 from the soil. All manures from organized substan- 

 ces contain the principles of vegetable matter, which 

 during putrefaction are rendered either soluble in 

 water or aeriform and in these states they are capa- 

 ble of being assimilated to the vegetable organs. No 

 one principle affords the pabulum of vegetable life ; 

 it is neither charcoal nor hydrogene, nor azote nor 

 oxygene alone ; but all of them together in various 

 states and various combinations. Organic substances 

 as soon as they are deprived of vitality, begin to pass 

 through a series of changes which end in their com- 

 plete destruction, in the entire separation and dissipa- 

 tion of the parts. Animal matters are the soonest des- 

 troyed by the operation of air, heat, and light. Vege- 

 ble substances yield more slowly, but finally obey the 

 same laws. The periods of the application of manures 



