LIGHT. 51 



and to extend the empire of their existence beyond the 

 li-nits of perpetual snow. They are furnished with 

 buds, which guard the tender leaves and flowers from 

 injury, till the period of their evolution arrives, after 

 which their power of self preservation is lost, and they 

 are injured by the cold which they are no longer pre- 

 pared to resist. 



8. LIGHT.— Another agent is light ; without which, 

 plants may be made to grow, but no longer exhibit the 

 verdure, the texture, or any of the properties of health. 

 Hereafter we shall probably learn, that while the at- 

 mosphere is contaminated by the respiration of ani- 

 mals, its purity is restored by the vegetation of plants. 

 But secluded from the light, vegetables are no longer 

 capable of converting a portion of the fixed air to their 

 own use, or of supplying the atmosphere with oxygen, 

 on which its importance to animal life, chiefly, if not 

 entirely depends. By the action of light, the carbon 

 of the fixed air is interwoven with the very texture of 

 the plant, whereby it acquires a greater degree of firm- 

 ness, and becomes more valuable in the arts. Through 

 its agency, the aromatic and essential secretions are 

 formed, and hence we find them existing in perfection, 

 only in countries which are favoured with the perpet- 

 ual light of summer, or on elevated mountains, where 

 the ra} r s of light meet with no obstruction. There we 

 find the Nutmeg, the Clove, the Cinnamon and the Pe- 

 ruvian barks, all designed to increase the comforts, or 

 diminish the sufferings of humanity ; and all owing 

 their chief excellencies to the light of the sun. 



When prepared to investigate the geographical dis- 

 tribution of the vegetable kingdom, we shall learn the 

 powerful effects of these united causes. Feeble and ex- 

 hausted in Polar regions, vegetation acquires strength 



