360 Dr George Buist on the 



of miles removed from them, their subjection is not the less 

 complete ; the vast volume of water, capable of crushing by 

 its weight the most stupendous barriers that can be opposed 

 to it, and bearing on its bosom the navies of the world, im- 

 petuously rushing against our shores, gently stops at a given 

 line, and flows back again to its place when the word goes 

 forth — " thus far shalt thou go, and no farther ;" and that 

 which no human power or contrivance could have repelled, 

 returns at its appointed time so regularly and surely, that 

 the hour of its approach, and measure of its mass, may be 

 predicted with unerring certainty centuries beforehand. The 

 hurricanes which whirl with such fearful violence over the 

 surface, raising the waters of the sea to enormous elevations, 

 and submerging coasts and islands, — attended as they are by 

 the fearful attributes of thunder and deluges of rain, — seem 

 requisite to deflagrate the noxious gases which have accu- 

 mulated — to commingle in one healthful mass the polluted 

 elements of the air, and restore it fitted for the ends designed 

 for it. It is with the ordinary, not with the exceptional, 

 operations we have at present to deal, and the laws which 

 rule the hurricane form themselves the subject of a treatise. 



We have hitherto dealt with the sea and air, — the one 

 the medium through which the commerce of all nations is 

 transported, the other the means by which it is moved along,— 

 as themselves the great vehicles of moisture, heat, and cold, 

 throughout the regions of the world — the means of securing 

 the interchange of these inestimable commodities, so that 

 excess may be removed to where deficiency exists, deficiency 

 substituted for excess, to the unbounded advantage of all. 

 We have selected this group of illustrations for our views, be- 

 cause they are the most obvious, the most simple, and the 

 most intelligible and beautiful, that could be chosen. Short 

 as our space is, and largely as it has already been trenched 

 upon, we must not confine ourselves to these. 



We have already said that the atmosphere forms a 

 spherical shell surrounding the earth to a depth which is 

 unknown to us by reason of its growing tenuity, as it is re- 

 leased from the pressure of its own superincumbent mass. 

 Its upper surface cannot be nearer to us than fifty, and can 



