258 rUYSICAL GEOGilAPHY OF TUE SEA, AND ITS METEOllOLOGY. 



exercise at least some degree of influence in disturbing equilibrium, 

 are not these creatures entitled to be regarded as agents which 

 have their offices to perform in the system of oceanic circulation, 

 and do they not belong to its physical geography? Their in- 

 fluences upon the economy of the sea are like those outstanding 

 quantities which the astronomer finds in the i)eriods of heavenly 

 bodies. He calls them perturbations ; for short, or even during 

 considerable intervals, their effects maybe inappreciable ; for they 

 are pendulums that require ages for a single vibration; but 

 unless there was a balance provided somewhere, they would, 

 during the jirogress of time, accumulate their small perturbations 

 so as to produce disorder, and finally cause the destruction of 

 worlds. So, too, with the salts of the sea, and those little micro- 

 scopic inhabitants of its waters. They take care of its outstand- 

 ing quantities of solid matter, and by their influence preserve 

 harmony in the ocean. It is immaterial how great or how small 

 that influence may be supposed to be ; for, be it great or small, 

 it is cumulative ; and we therefore may rest assured it is not a 

 chance influence, but it is an influence exercised by design, and 

 according to the commandment of Him whose "voice the winds 

 and the sea obey." Thus God speaks through sea-shells to the 

 ocean. 



488. TlLeir ][jhysical relations. — It may therefore be supposed 

 that the arrangements in the economy of nature are such as to 

 require that the various kinds of marine animals, whose secretions 

 are calculated to alter the specific gravit}'- of sea water, to destroy 

 its equilibrium, to beget currents in the ocean, and to control its 

 circulation, should be distributed according to order. Upon this 

 supposition — the like of which Nature warrants throughout her 

 whole domain — we may conceive how the marine animals of 

 which we have been speaking may impress other features upon 

 the ph^'sical relations of the sea by assisting also to regulate cli- 

 mates, and to adjust the temj)erature of certain latitudes. For 

 instance, let us suppose the Avaters in a certain part of the torrid 

 zone to be 90^, but, by reason of the fresh water which has been 

 taken from them in a state of vapour, and consequently by reason 

 of the proportionate increase of salts, these waters are heavier 

 than waters that maybe cooler, but not so salt (§ 105). This 

 being the case, the tendency would be for this warm, but salt and 

 heavy water to flow off as an under current towards the polar or 

 some other regions of lighter water; but these creatures take 



