INTRODUCTION. VH 



ter may attract matter at all distances from zero to infinity. 

 This attraction takes place with a force varying directly in 

 proportion to its quantity, and inversely as the square of the 

 distance. Now when matter collects into masses, as we see 

 it has done in the case of the starry heavens and planetary 

 bodies, two or more bodies, thus mutually attracting each other, 

 separate sometimes to distances all but infinite, but according 

 to a fixed and determinate mathematical law, the distance 

 being in exact proportion to the ratio of their respective mag- 

 nitudes and quantities of matter. We call the name of this 

 species of attraction, gravity. But when matter retains its 

 elementary condition, and exists in the form of those invisible 

 particles called atoms, two or more mutually attracting par- 

 ticles must be brought by the same law infinitely near to 

 each other before they can exercise any mutual influence; 

 and we give the name of clieniical affinity to this kind of at- 

 traction. 



To apply this philosophy to plants. They are the result, 

 principally, of the atomic or chemical affinity, comhined with 

 other agents, and are a beautiful pile of matter borrowed from 

 the atoms in the earth and air, and united together by the 

 operation of natural laws for a little space of time. Fabricated 

 by nature as material for the building up of higher or- 

 ganic forms, they perform their part in the ever-shifting 

 scenery of life, and either become incorporated as food into 

 animal bodies, or else, retaining their state as plants, they are 

 the instruments used by nature to extract fertilizing princi- 

 ples from every falling shower and passing breeze, which they 

 impart to the soil on which they finally decay. The end of 



