19-1 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY. 



404. Vertical cii'culation is as important in the sea as it is in 

 The compressibility the air (§231). In striving to understand the 

 m S'?c7an^c dr°-^ physical machinery of om: planet and to compre- 

 cuiation. hend its workmgs, we miist, il we would learn, pro- 



ceed upon the principle (§ 351) that at creation the waters were 

 measured, the hills weighed, and the atmosphere meted out, and 

 that each was endowed with its peculiar properties so proportioned 

 and so adjusted as exactly to answer its purposes in the grand 

 design. • And, consequently, we are entitled to infer that fluidity 

 instead of solidity was imparted to a certain quantity of matter 

 which we call water, to enable it to perform the offices to be re- 

 quired of fluid matter, and which, in the terrestrial economy, solid 

 matter was not adapted to perform. By this mode of reasoning 

 we are taught to regard the fluidity of all the water in the sea as 

 a physical necessity — and by this mode of reasoning we are re- 

 quired to reject as insufficient, any hypothesis touching the sys- 

 tem of aqueous circulation on our planet which ignores, even in 

 the profoundest depths of the ocean, an interchange of its parti- 

 cles between the bottom and the top. Were such interchange 

 not to take place — were the water in the sea which once sinks be- 

 low the level of its horizontal circulation doomed to remain there 

 for ever, it would not be difficult to show that the sea would lose 

 its balance and its counterpoises ; that, not being able to preserve 

 its status, the water at the bottom would have grown heavier and 

 heavier, while that at the top would have beco:ne lighter and 

 lighter, until the one became satm*ated with salt, the other entirely 

 fresh. To prevent this state of things, we recognize the in- 

 fluences of the winds and tides, as well as the necessity of vertical 

 movements in the sea. Whence, therefore, let us inquire, when 

 a given quantity of water once finds its way to the bottom of the 

 sea, whence — since it goes there by virtue of its ovim specific gravity, 

 whence is power to be derived for bringing it up again ? tor 

 sooner or later, according to this view, up it must come. We thus 

 arrive precisely at one of those points (§ 287) at which hypothesis 

 becomes absolutely necessary ii' we would make fui'ther progress. 

 Here, therefore, let us pause to search among the physics of the 

 sea for such a pov/er and the foundation for hypothesis. LesHe 

 has pointed out exactly such a power for the atmospheric ocean, 

 — a power which, after the heaviest air has settled at the bottom 

 of its subtile sea — after the lightest has come to rest at the top, 

 and, the whole arranged itself according to specific gravity — can 



