100 Prof. Trowbridge on Deep-sea Soundings. 



error in height of one or two miles is unimportant, or that the 

 elevations of oi'dinary 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 unfathom- 

 able depths, stands the sounding of Captain Denham of the 

 British Navy, in H.IM.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 

 costs of the lead vjhich 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 regard to them, except that they 

 gave no I'esult. The sounding of Captain Denham was made 

 with a lead weighing nine pounds, attached to a line one-tenth 

 of an inch in diameter ; and it is reported that this lead descended 

 to the depth of nearly nine miles in the sea without touching 

 bottom. 



In accordance with a plan which originated with the lamented 

 G. M. Bache, United States Navy, in 1846, in the explorations of 

 the Gulf-stream, and which has constantly been followed since. 

 Captain Denham noted the time of running out of the successive 

 portions of the sounding-line during the nine hours of its sup- 

 posed descent. According to these observed times of descent, 

 the nine-pound lead communicated to the descending line at the 

 depth of 3000 fathoms, or 18,000 feet, a velocity of two feet per 

 second ; a result which is philosophically impossible, since the re- 

 sistance of the water acting upon a line of this diameter, moving 

 with a velocity of two feet per second, at the depth mentioned, 

 amounts to more than three times the weight of the lead or shot 

 used. It will hardly be necessary to enter into any argument to 

 show that there can be no motion of descent when the resistance 

 to that motion is three times the weight of the moving mass. 

 Further, the observations show that the nine-pound shot and line 

 were running with a velocity of two feet and a half per second 

 at the depth of 2000 fathoms, or 12,000 feet. Here the result 

 contradicts in quite as strong a manner the mechanical laws of 

 the descent ; and in fact below 1000 fathoms, or 6000 feet, if 

 we credit the observations, a velocity was observed in the running- 

 out of the line which it was impossible for the lead to communi- 

 cate to it. In fact but a small part of that velocity could have 



* Lieut. Maury discusses these deep casts in his sailing directions j but his 

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



