Prof. Trowbridge on Deep-sea Soundings. 99 



In the succeeding year, in the same explorations^ soundings were 

 made to the depth of 1500 and 3160 fathoms, without finding 

 bottom : but in the latter case the temperature of the water was 

 recorded at the depth named. In 1848, in the explorations off 

 Cape Hatteras, the officer engaged in the explorations lost his 

 instrument, with 3300 fathoms of line out. 



These Gulf-stream explorations were undoubtedly the first 

 systematic deep-sea explorations ever undertaken. 



Our principal object, however, is to notice those great depths 

 where no bottom was found, and to examine whether the failure 

 to find the bottom was, under the circumstances, any proof that it 

 did not exist at much less depths than those reported, or whether 

 any conclusion whatever can be derived from the results. 



When we reflect that two-thirds of the earth^s surface is co- 

 vered with water, while the remaining third is dry land, and 

 that the figure of the solid part can only be known when we 

 can trace with certainty the mountain-ranges and valleys along 

 the bottom of the sea, it becomes important to scrutinize those 

 reported measurements which give such enormous depressions 

 in different parts of the sea, compared with which the highest 

 mountain-ranges are insignificant elevations. Numerous in- 

 stances have been reported in which soundings have been made 

 to the depth of five, six, seven, eight, and nine miles without 

 finding bottom ; and again over large areas the bottom of the 

 sea is represented as a comparatively level plain submerged to 

 the depth of two, three, or four miles. Supposing these reported 

 measurements to have been correct, we should have still very 

 insufficient data for arriving at any correct conclusions with 

 regard to the elevations and depressions of the ocean-bed. What 

 idea could be formed, for instance, of the topography of our 

 country, if our knowledge of its surface consisted in knowing 

 the height, above the level of the sea, of only one point in every 

 State of the Union. Such points, selected at random, might be 

 the highest or lowest points within an area of some thousands 

 of square miles ; and after all, we should only know that it was 

 possible to measure those heights, without being able to conjec- 

 ture even their relation to each other. In the case of deep-sea 

 soundings, we only know that bottom has been reached, — in some 

 instances at depths which show that our ideas concerning the 

 unfathomable abysses of the ocean have been erroneous, and to 

 sustain the belief that the mean depth is less than has been sup- 

 posed. With regard to the uncertainties of the measurements, 

 it is not sufficient to say that, compared with the immense area 

 over which they are spread, the depths are very small ; it might 

 as well be argued that the height of the Alps is insignificant 

 . compared with the distance around the earth, and therefore an 



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