l6o THE WEATHER, AND WEATHER PROPHETS. 



at whatever part of the globe it happens to be vertical, 

 and at which there is a supply of moisture, and foi 

 a very large space around it ; what may be likened 

 to a vast up-surging fountain of air and vapour tlirow- 

 ing itself up with an impetus ; breaking up and bulg- 

 ing outwards the immediately incumbent aerial strata 

 very far above their natural levels ; and introducing 

 at the same time into the air a great quantity of va- 

 pour, as well as withdrawing, by direct transfer, from the 

 lower atmosphere, a great deal of air; which of course 

 has to be supplied by in-draft along the surface of the 

 earth. 



(23.) The process now described, is in a great many 

 of its features similar to that gentler one previously 

 stated : and as it always takes place at some point 

 or other of the intertropical region, it conspires with 

 and locally exaggerates its result so far as the transfer 

 and circulation of air and the production of winds is 

 concerned. As regards the vapour, a large portion is 

 very speedily deprived of its elasticity and ascensional 

 power, and reduced to the state of visible cloud, col- 

 lecting and descending in rain. This is a consequence 

 partly of its arrival in a colder region, but mainly of the 

 property which all gases and all vapours alike possess, 

 of absorbing and rendering latent a large quantity of 

 heat as they expand in volume, and so becoming, ipso 

 facto, colder. Both the air and the vapour do so expand 

 as they rise, by reason of the diminution of pressure they 

 experience. The air indeed retains its elastic state as 

 air, however cold it may become ; and therefore merely 



