°29 
LECTURE II. 
OF THE GENERAL POWERS OF MATTER WHICH INFLUENCE 
VEGETATION. OF GRAVITATION, OF COHESION, OF CHE- 
MICAL ATTRACTION, OF HEAT, OF LIGHT, OF ELEC- 
TRICITY, 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, sub- 
mitted to these laws ; and it is necessary to study 
their effects, both in considering 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 
masses 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. 
