208 DESCENT OF VAPOUR. 



be raised straight and the inequalities of the ends 

 to be arranged, in order to have a very clear notion 

 of what it would be if the causes of disturbance 

 were removed. 



The descent of a cloud, of a column of cold air, 

 or of any thing else that can be so dispersed 

 through the atmosphere, is just the reverse of its 

 ascent ; and therefore its form, if it were visible 

 and undisturbed, would be hyperbolic, only with 

 a downward motion, in place of an upward one, as 

 in the former case. The motion would, however, 

 be more rapid ; and for that reason the descend- 

 ing hyperbolic mass would converge, or come to- 

 gether, more rapidly than the ascending one 

 spreads. It is true that as it descended it would 

 meet with more resistance from the denser air ; 

 and also from the upward current of air and of 

 heat from the earth's surface, if the place under it 

 happened to be warm ; but still the weight of the 

 descending matter itself, the velocity it had ac- 

 quired in descending, and the attraction of cohesion 

 between its own particles, or portions, would all 

 act in favour of the descent and the convergence, 

 whereas they act in opposition to the ascent and 

 the spread. Were that not the case, we should 

 haye water rising in showers, just as often as it 

 falls in showers, or, to speuk more correctly, there 

 would neither be the one nor the other ; because, 

 wherever it happened to be, the water would re- 

 main quite stationary. 



To understand well how nature works, it is ab- 

 solutely necessary to have clear and perfect views 

 of what may be called her elementary working, 

 that working in which there is no organization of 

 parts, and no individual substance which we can 



