4. 



situation is ovon moro unsatisfactory for tho loss frcquontod mrts 

 of the world. Existing soundings, to quote a specific cxarnplo, do 

 P°L^^i°3 ^^tisfactory mapping of tho shape of the bottom of the' 

 Gulf^of Maine, _a region made physlographically interesting for tho 

 glacial geologist by its submarine troughs and banks. Even within 

 the past year one of the main channels leading into one of its 

 larger tributaries (Passamaquoddy Bay) has been found considerably 

 deeper than had previously been supposed. 



A multiplication of soundings in depths grcitcr than 100 

 fathoms is absolutuly^ necessary if the geologist is to discover what 

 becomes of the geologic structures as they plunge into the seat and 

 It IS obvious that much of our philosophy regarding mountain rang s 

 IS dependent on their submarine continuations. '"c might call atten- 

 tion especially to the inadequacy of existing soundings to show tho 

 fault scarps believed to exist along the northern slope of South 

 America, or to outline the und.r-sca contours of the Caribbean vol- 

 canic arcs and of tho outer Bahamas. 



The difficulty is not one of inaccuracy of observation, --on the 

 contray, the soundings taken by all the important maritime nations 

 have long boon extremely exact - but of their comparative scarcity 

 everywhere outside the 50-fathom contour, l/c must remember that 



.?.^2, 2°^n'^lngs marked on the chart may seem frequent enough, in 

 reality ^ they may be many miles apart. Furthermore, as they have been 

 i.aken with the needs of navigation constantly in mind, it often 

 happens that just those regions whore tho geologist needs tho closest 

 survey have been the most neglected, while the approaches to harbors 

 etc., that have bc.en the most carefully sounded, may be the least 

 interesting stretches of bottom, scientifically considered. 



Tho case is far worse for th^; ocean basins, where we owe 

 practically all our knowledge of the depth, away from tho slopes of 

 the continents, to the occasional doep-soa exploring expeditions, to 

 the surveys made along routes thought suitable for submarine cables, 

 and^to scattering data from other sources. Of th^se throe sources 

 of iniormation, cable surveys alone, and a few lines recently sur- 

 veyei with sonic depth-finders, have yielded data at all comparable, 

 m closeness, with the surveys that have boon made of shoal v/aters . 

 The result has been that OL7.r knowledge of tho sea floor is still of a 

 very generalized sort. And the contour lines laid dovm on the b^thy- 

 metric charts of the oceans are equally generalized, located on the 

 assumption that submarine slopes are as a rule so gentle that if 

 soundings are _ taken every couple of hundred miles th^y will pro'n-bly 

 reveal the existence of any important ridges or troughs. But r.-cmt 

 soundings by the "Meteor", by the U. S. Navy, and those now being 

 carriea out by the ''Carnegie" prove that this assumption is not as 

 sound as was formerly supposed. 



The North Atlantic is, naturally, the best known ocean bathy- 

 metrically. There is no reason to suppose that oven such detailed 

 examination as is now possible with sonic methods will seriously 

 alter the existing picture of it. Even in the North Atlantic, how- 

 ever, we still lack detailed knowledge about tho important deeps 

 north of Porto I^ico, and in the Caribbean. i.-'e have recently learned 

 that the representation on the charts, of the slopes of the Grand 



