276 



LECTURE VII. 



On Manures of mineral Origin, or fossile Manures ; 

 their Preparation^ and the Manner in which they 

 Act. Of Lime in its different States ; Operation of 

 Lime as a Manure and a Cement ; different Combin- 

 ations of Lime. Of Gypsum ; Ideas respecting its 

 Use Of other Neutro-s aline Compounds, employed as 

 Manures. Of Alkalies and alkaline Salts ; of Com- 

 mon Salt. 



THE whole tenor of the preceding Lectures 

 shews, that a great variety of substances contributes 

 to the growth of plants, and supplies the materials of 

 their nourishment. The conversion of matter that 

 has belonged to living structures into organised 

 forms, is a process that can be easily understood ; but 

 it is more difficult to follow those operations by which 

 earthy and saline matters are consolidated in the fibre 

 of plants, and by which they are made subservient to 

 their functions. Some enquirers adopting that sublime 

 generalization of the ancient philosophers, that matter 

 is the same in essence, and that the different substan- 

 ces considered as elements by chemists, are merely 

 different arrangements of the same indestructible par- 

 ticles, have endeavoured to prove that all the varieties 

 of the principles found in plants, may be formed from 



