32 



sta.ndpoint, very little is yet known (except for shoal waters) abo-at 

 the absolute depths to which it is effective. For example, canve 

 assume as representative of the sub-tropical belt of the Atlantic as 

 a whole the conditions prevailing on the Challenger Bank, off Bermuda, 

 where storn waves roll considerable masses of calcareous algae to and 

 fro, often enough for these to stay alive on all sides, down to a 

 depth of 50 fathoms or so? How much deeper is effective wave-base 

 in the Antarctic vihexe swells might theoretically, travel right 

 around the globe without meeting any obstacle - and perhaps actually 

 do so? What is the actual speed of such oscillation at different 

 depths, when set in motion by storm waves of different shapes, 

 lengths, etc., and travelling at different speeds? For that matter 

 the shapes and run of the surface waves themselves offer an interest- 

 ing field; in fact the stereogrammic studies by recent expeditions, 

 notably those of the "Meteor" have given the first exact topographic 

 pictures of the very coiioplex corrugations into which the surface of 

 the sea is thrown by the wind. 



Our present knowledge of submarine boundary (or internal waves 

 in the open oceans has hardly advanced beyond the realization that 

 such things erist, and that they nay be set up by a variety of 

 forces. Vj'e need to learn what conditions give rise to progressive 

 boundary waves, what conditions to standing waves; their periods; 

 their relation to the free tidal v^ave; and their role in general in 

 the sea, including such points as their frequency in different 

 regions at different seasons, their vertical amplitudes, their 

 lengths from crest to crest, etc. 



Perhaps the most pressing of the broad problems in physical 

 oceanography today, made so by its direct bearing, not only on 

 events of all sorts in the sea, but on land-climates as well, is 

 that of the irregular fluctuations of the ocean currents, with the 

 causes of such events. 



It is C'-!rtain that if the present scheme of ocean circulation 

 were materially to change, the climates of the continents would soon 

 differ widely from the present stare; and for the worse, so far as 

 man's welfare is concerned. The effect of the ocean currents on 

 land climates is so much a commonplace, stressed in every textbook 

 of physical geography or meteorology, that we need only cite (a 

 classic example) the effect of the Gulf Stream or North Atlantic 

 drift, making habitable the most northerly parts of western Europe, 

 (reflected in the fact that the mean temperature for January is 

 about 40° F. higher in Northern Norway than is normal for that 

 latitude), contrasted with the oioposite side of the Atlantic, where 

 the icy Labrador current from the North chills the climate of the 

 coastal strip all along Labrador and Newfoundland, making agricul- 

 ture impossible at latitudes corresponding to those of Ireland and 

 England. Any variations in the currents that shift the previously 

 existing distribution of temperature in the sea, as any considerable 

 alteration is bound to do, will have a still more direct bearing on 

 animal and plant life in the sea; one almost certainly destructive 

 to soma species, but perhaps temporaril^r favoring the production, or 

 extending the geographic boundaries of others. Cases in point are 

 the almost total destruction of the tile fish off the east coast 

 of the United States in 1334, presumably by a flooding with cold 

 water, and the ir-miigration of fishes of temperate thermal affinities 



