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LECTURE II. 



Of the general Powers of Matter which influence Vegeta- 

 tion. Of Gravitation, of Cohesion, of chemical Attrac- 

 tion, of Heat, of Light, of Electricity, ponderable 

 Substances, Elements of Matter, particularly those 

 found in Vegetables, Laws of their Combinations and 

 Arrangements. 



THE great operations of the farmer are directed 

 towards the production or improvement of certain 

 classes of vegetables ; they are either mechanical or 

 chemical, and are, consequently, dependant upon the 

 laws which govern common matter. Plants themselves 

 are, to a certain extent, submitted to these hws ; and 

 it is necessary to study their effects both in consider- 

 ing the phenomena of vegetation, and the cultivation 

 of the vegetable kingdom. 



One of the most important properties belonging 

 to matter is gravitation, or the power by which mas- 

 ses of matter are attracted towards each other. It is 

 in consequence of gravitation that bodies thrown into 

 the atmosphere fall to the surface of the earth, and that 

 the different parts of the globe are preserved in their 

 proper positions. Gravity is exerted in proportion to 

 the quantity of matter. Hence all bodies placed above 

 the surface of the earth fall to it in right lines, which 

 if produced would pass through its centre ; and a 



