260 THE PHYSICAL GEOGRAPHY OF THE SEA. 



744. The microscope, under the eye of Ehrenberg, has enabled 

 us (§272) to put tallies on the wings of the wind, to learn of them 

 somewhat concerning its " circuits." 



745. Now may not these shells, which were so fine and impal- 

 pable that the officers of the Dolphin took them to be a mass of unc- 

 tuous clay — may not, I say, these, with other specimens of sound- 

 ings yet to be collected, be all converted by the microscope into 

 tallies for the waters of the different parts of the sea, by which the 

 channels through which the circulation of the ocean is carried on 

 are to be revealed ? 



746. Suppose, for instance, that the dwelling-place of the little 

 shells which compose this specimen from that part of the ocean be 

 ascertained, by referring to living types, to be the Gulf of Mexico 

 or some other remote region ; that the habitat and the burial-place, 

 in eveiy instance, be far removed from each other — by what agen- 

 cy, except through that of currents, can we suppose these little 

 creatures — themselves not having the j)Owers for more than a very 

 restricted locomotion — to come from the place of their birth, or 

 to travel to that of their burial ? 



747. Man can never see — he can only touch the bottom of the 

 deep sea, and then only with the plummet. Whatever it brings 

 up thence is to the philosopher matter of powerful interest ; for by 

 such information alone as he may gather from a most careful ex- 

 amination of such matter, the amount of human knowledge con- 

 cerning nearly all that portion of our planet which is covered by 

 the sea must depend. 



748. Every specimen of bottom from the deep sea is, therefore, 

 to be regarded as probably containing something precious in the 

 way of contribution to the sources of human knowledge ; and each 

 as it is brought up will be viewed with increasing interest, and will 

 suggest to us thoughts more and more profitable concerning the 

 wonders of the deep. 



749. " There has been sent," says Brooke, in a letter from the 

 Surveying Expedition of the North Pacific, " a table of tempera- 

 tures at various depths, from one hundred to five hundred fathoms, 

 and two reports of experiments in deep-sea soundings. Several 

 unsuccessful attempts to sound from the ship were made under the 



