210 VARIATIONS OF COHESION. 



tation alone, the same quantity of water, when it 

 reaches the surface, will have only about one -fourth 

 more gravitation than it would have at the height 

 of fifty miles. 



It is very different with the cohesion, or as it is 

 called when the substances are not touching each 

 other, the attraction of cohesion, because the cen- 

 tre of that is in the body itself ; so that, whenever 

 from any cause, and that cause may be generally, 

 if not invariably, said to be a cooling, or suspen- 

 sion of heat, the moisture in any part of the air 

 becomes more dense than that in the surrounding 

 parts, the centre of that part instantly becomes a 

 centre of cohesion ; and those particles of water 

 which are situated at half the distance have four 

 times as much tendency towards that centre, and 

 so on for all other distances. 



Thus we see that the tendency of moisture in 

 the air to form a cloud is much greater than the 

 tendency of that cloud to fall after it is formed ; 

 and that it is so without reference to any thing 

 else than the three principles of gravitation, cohe- 

 sion and heat, principles which, in themselves, 

 contain the abstract of the whole philosophy of 

 matter. It is not unusual to call in at this stage 

 of the business the assistance of ideal causes, much 

 after the same fashion as those who know not the 

 true God worship idols, or those who are ignorant 

 of the truth give currency to any untruths; but 

 the careful observer of nature should be especially 

 on his guard against false causes ; for it is in them 

 that all error in the knowledge of nature lies. It 

 has not been unusual to delegate the process of 

 cloud-making to electricity, to magnetism, and to 

 the aurora-borealis ; but in all probability, though 



