286 ANNUAL OF SCIENTIFIC DISCOVERT. 



Our principal object, however, is to notice those great depths where no 

 bottom u-as 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 covered 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 moun- 

 tain-ranges and valleys along the bottom of the sea, it becomes important 

 to scrutinize those reported measurements which give such enormous de- 

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

 mountain-ranges are insignificant elevations. Numerous instances 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 would 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 sur- 

 face 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 would only know that it was possible to 

 measure those heights, without being able to conjecture, 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 supposed. 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 error in height of one or two miles is unimpor- 

 tant ; or that the elevations of ordinary mountain-ranges need not be 

 noticed when compared with the area of a continent. We are dealing with 

 finite quantities, not with the infinite with which they may be compared; 

 and an error of several thousand feet in two or three miles is hardly within 

 the limits of scientific accuracy. 



Prominent among the instances of these reported unfathomable depths, 

 stands the sounding of Captain Denham of the British navy, in H. M. S. 

 Herald, made in October 1852, on a voyage from Rio de Janeiro to the Cape 

 of Good Hope. This is an extreme case ; but since it is reported among the 

 greatest deep-sea casts, it will serve best for illustration.* All other great 

 casts of the lead which have been reported are subject to the same causes 

 of error which are to be found in this, some in a greater and some in a less 

 degree ; so that it is not necessary for us to believe, yet, anything with 



is the one labelled No. 1, latitude 33 04' 40", longitude 73 56' 47", 90 fathoms. 

 This is crowded with Folytlialamiaa forms, mostly large enough to be recognized 

 by a practised eye without the aid of a magnifier. 



* Lieutenant Maury discusses these deep casts in his sailing directions, but his 

 rules for arriving at the depth, do not seem to me to be entirely satisfactory. 



