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HYDROGRAPHY. 



As we ascend from the surface, as gravitation decreases, we believe 

 that the atmosphere of vapor is retarded, or falls behind ; or that the 

 earth slips from under it, leaving it to the west. If this is so, the 

 several meteorological phenomena connected with vapor can be readily, 

 simply, and, we think, satisfactorily, explained. 



.The phenomenon of rain, it is well known, is produced by the com- 

 mingling of two masses of atmosphere of different temperatures, when 

 precipitation takes place. This is more or less copious, according to 

 the quantity of moisture or vapor Avhich is held in suspension by them.' 

 The question as to how this vapor is carried, and whence it is brought, 

 and how so equally divided, has excited the curiosity and admiration 

 of all. 



It has been very naturally supposed that the clouds transport this 

 moisture from one place to another; but, when we come to investigate, 

 they are but the outward evidence that there is vapor in the atmo- 

 sphere : the immense quantity of rain which falls, and the small 

 amount which the clouds can hold suspended, satisfies us that but a 

 part of the vapor can be borne by the clouds, and that the large sup- 

 ply must be held suspended in the atmosphere : though invisible, we 

 know it exists there. 



We do not entertain the opinion that the clouds, carried by the cur- 

 rents of air, can bear the moisture or rain from distant regions to fer- 

 tilize a country ; the local influences prevailing on the route would 

 controvert, in our opinion, such a theory ; it would be impossible for 

 so large a quantity of water as frequently falls to remain so long sus- 

 pended in the form of vapor through the various climates, without 

 undergoing condensation and precipitation ; and the time necessary to 

 transport it, under the ordinary velocity of the winds, forbids it ; 

 besides, the supply would be at all times precarious, from the varying 

 temperature of the climates which it would have to pass through on 

 its transition from one parallel to another. On this account, and for 

 other reasons, it seems impossible to subscribe to the theory of " rain- 

 bearing winds." It must be distributed in other ways. 



We have already referred to the distribution of vapor under its own 

 law, and can readily account for the supply of rain ; nor are we at a 

 loss to point out the reservoir which affords such copious supplies. 



The evaporation from the great oceans whence the supply of vapor 

 comes, takes place at all seasons of the year, particularly when the 

 sun is vertical. It flows to the west, under its law of distribution, 



