AND OF THE OTHER BODIES OF SPACE. 21 



latter. A fourth being added, the third will perhaps leave 

 the first, and join the new comer. 



Such is an outline of the information which chemistry 

 gives us regarding the constituent materials of our globe, 

 and their combinations. How infinitely is the knowledge in- 

 creased in interest, when we consider the probability of such 

 being the materials of the whole of the bodies of space, and 

 the laws under which these everywhere combine, subject only 

 to local and accidental variations ! 



In considering the cosmogenic arrangements of our globe, 

 our attention is called in a special degree to the moon. 



In Laplace's hypothesis, satellites are considered as masses 

 thrown off from their primaries, exactly as the primaries had 

 previously been from the sun. The orbit of any satellite is 

 also to be regarded as marking the bounds of the mass of the 

 primary at the time when that satellite was thrown off; its 

 speed likewise denotes the rapidity of the rotatory motion of 

 the primary at that particular juncture. For example, the 

 outermost of the four satellites of Jupiter revolves round his 

 body at the distance of 1,180,582 miles ; hence, according to 

 the hypothesis, the planet was once about 3,675,501 miles in 

 circumference, instead of being, as now, only 89,170 miles in 

 diameter. This large mass would take rather more than six- 

 teen days six hours and a half (the present revolutionary 

 period of the outermost satellite) to rotate on its axis. The 

 innermost satellite would be formed when the planet was re- 

 duced to a circumference of 309,075 miles, and rotated in 

 about forty- two hours and a half. 



From similar inferences, it would result that the mass of 

 the earth, at a certain point of time after it was thrown off 

 from the sun, was no less than 482,000 miles in diameter, 

 being sixty times what it has since shrunk to. At that time, 

 the mass must have taken rather more than twenty-nine and 

 a half days to rotate, (being the revolutionary period of the 

 inoon,) instead of, as now, rather less than twenty-four hours. 



The time intervening between the formation of the moon, 

 and the earth's diminution to its present size, was probably 



