LAWS OF HEAT. AIR. 109 



as enter into the constitution of the atmosphere, 

 is one manifestly of much greater complexity, 

 and indeed to us probably of insurmountable 

 difficulty as a mechanical problem. But all that 

 investigation and analogy teach us, tends to show 

 that it will resemble the other problem in the 

 nature of its result; and that certain relations 

 of its data, and of the laws of its elements, are 

 necessary requisites, for securing the stability of 

 its mean condition, and for giving a small and 

 periodical character to its deviations from such a 

 condition. 



It would then be probable, from this reflexion 

 alone, that in determining the quantity and the 

 law and intensity of the forces, of earth, water, 

 air, and heat, the same regard has been shown to 

 the permanency and stability of the terrestrial 

 system, which may be traced in the adjustment 

 of the masses, distances, positions, and motions 

 of the bodies of the celestial machine. 



This permanency appears to be, of itself, a 

 suitable object of contrivance. The purpose for 

 which the world was made could be answered 

 only by its being preserved. But it has ap- 

 peared, from the preceding part of this and the 

 former chapter, that this permanence is a per- 

 manence of a state of things adapted by the most 

 remarkable and multiplied combinations to the 

 well-being of man, of animals, of vegetables. 

 The adjustments and conditions therefore, beyond 



