212 THEORY of the EARTH. 



, WE have an irregular body of land, raifed above the 

 level of the ocean. This, no doubt, is the fmallefl portion of 

 the globe ; but it is the part to us by far moft interefting. It 

 is upon the furface of this part that plants are made to grow j 

 confequently, it is by virtue of this land that animal life, as 

 well as vegetation, is fuftained in this world. 



Lqftly, WE have a furrounding body of atmofphere, which 

 completes the globe. This vital fluid is no lefs neceflary in the 

 coaflitution of the world than are the other parts j for there is 

 hardly an operation upon the furface of the earth, that is not 

 conducted or promoted by its means. It is a neceflary condi- 

 tion for the fuflenance of fire ; it is the breath of life to ani- 

 mals ; it is at leaft an inflrument in vegetation j and while it 

 contributes to give fertility and health to things that grow, it 

 is employed in preventing noxious effects from fuch as go into 

 corruption. In Ihort, it is the proper means of circulation for 

 the matter of this world, by raifing up the water of the ocean, 

 and pouring it forth upon the furface of the earth. 



SUCH is the mechanifm of the globe; let us now mention 

 fome of thofe powers by which motion is produced, and activi- 

 ty procured to the mere machine. 



FIRST, There is the progrefiive force, or moving power, by 

 which this planetary body, if folely actuated, would depart 

 continually from the path which it now purfues, and thus be 

 for ever removed from its end, whether as a planetary bo- 

 dy, or as a globe fuftaining plants and animals, which may be 

 termed a living world. 



BUT this moving body is alfo actuated by gravitation, which 

 inclines it directly to the central body of the fun. Thus it is 

 made to revolve about that luminary, and to preferve its path. 



IT is alfo upon the fame principles, that each particular part 

 upon the furface of this globe, is alternately expofed to the in- 

 fluence of light and darknefs, in the diurnal rotation of the 

 earth, as well as in its annual revolution. In this manner are 



produced. 



