86 Progressive Changes of Matter. [Feb., 



shower, is soon dried by a brisk wind. Water that is neither 

 exposed to the sun's ray nor to the winds, wastes away, but 

 slowly however. We may, perhaps, account for this difference 

 upon mathematical principles. Suppose a surface of water to be 

 a foot square, and to be in the bottom of a tube exposed to the 

 air, but not to the wind or sun; and a like surface passed over by 

 a wind, it is evident that the latter is exposed to a greater surface 

 of a decomposing air in a given time; or in another form of ex- 

 pression, as soon as the particles of water mingle with the air, 

 they are swept away with the current: whereas in the tube they 

 would be sometime in ascending into a free air. There is another 

 process by which the evaporation of water is greatly facilitated. 

 The dashing of sea waves against the rocks, the cascades and 

 cataracts of rivers and the falling of rain drops through the 

 atmosphere. The water in these forms being subjected to such 

 rapid movements that it becomes pulverized, and so rapidly are its 

 elementary particles separated in a given time and space, that it 

 rises in form of fogs and spray. In these dashings of the water 

 a greater surface is exposed, and persons in some countries have 

 profited by an observance of this fact in the manufacture of salt, 

 by permitting salt water to pass down numerous small sticks or 

 wickers, by which the water readily escapes, leaving the salt ad- 

 hering to the faggots. Why may we not embrace the same 

 views by way of comparison relative to a mechanical suspension 

 in an atmospheric fluid, as in a watery liquid. A rock is heavier 

 than water of equal bulk, and readily sinks in it. But when it 

 is finely pulverized, the mass is held in suspension, provided there 

 be a current of water. This is owing to the greatly increased 

 surface or exposure of the parts to the water. That the aggre- 

 gate surface of these particles is infinitely greater than that of 

 the original mass, will become apparent by a moment's reflection : 

 suppose the rock to be two feet in diameter, then by taking ofT 

 one inch of its surface you make two new surfaces, thereby in- 

 creasing the surface of the entire mass nearly two fold; but when 

 you come to grind the entire mass to powder, you then increase 

 the aggregate surface beyond computation. Salt is heavier than 

 water and readily sinks in it, but water being its solvent the par- 

 ticles are soon held in suspension; and when the water becomes 

 pulverized, the particles being lighter than the particles of salt, 

 the formei- are cari'ied away by the atmosphere, leaving the latter 

 to re-combine into Iheir original form. Fill a vat with a com- 

 pound of bullets and corks, and pass a current of water over it, 

 and by agitating the mass, you would perhaps have an analogous 

 illustration of the manner in which the air separates water from 

 salt. But whether our views are correct or not, one thing is cer- 

 tain, that immense quantities of water in an invisible state are 

 daily passing into the air, and in due time returned again to the 

 earth. 



