GEOLOGY. 287 



regard to them, except that they gave no result. 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, U. S. X., in 1816, in the explorations of the Gulf Stream, and which 

 has constantly been followed since, Captain Denham noted the time of run- 

 ning out of the successive portions of the sounding-line during the nine 

 hours of its supposed 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 resistance 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 run- 

 ning 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 fath- 

 oms, 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 com- 

 municate to it. In fact, but a small part of that velocity could have been 

 produced by the descent of the lead. Here we have a reliable result to the 

 depth of 1000 fathoms only. The difference between this result and the 

 conclusions of Captain Denham is simply the difference between one mile 

 and nine miles. 



In measuring the distance to the sun, an error of eight miles would hardly 

 he worth noticing, perhaps; but what conclusions can be drawn from a 

 measurement in which the probable error amounts to eight times the whole 

 distance ? 



Popular ideas with regard to the sinking of bodies in the sea have here- 

 tofore been vague; for the reason, perhaps, that the laws which govern 

 this descent, and which are derived from the well-known laws of fluids, 

 have never been fully defined in their application to the depths of the 

 ocean. Some imagine that ships which founder at sea sink to a certain 

 depth and then float about until broken to pieces, or thrown upon some 

 bank beneath the sea; and, indeed, a recent writer in England has pub- 

 lished a book sustaining this absurd notion. Others, again, believe that 

 the buoyant force of the water at great depths is enormous, and clue to the 

 whole pressure of the column of water above, and that all bodies which are 

 lighter than water at the surface, will, if sunk to the bottom and detached 

 from the sinker, shoot upward with a great velocity ; or, in other words, 

 that the density of the water increases directly with the depth. These views 

 are erroneous. It is true the pressure increases with the depth, to the 

 amount of fifteen pounds upon every square inch for every thirty-four feet 

 in depth ; but the density is not thereby sensibly increased, owing to the 

 incompressibility of the water; so that neither the buoyant force nor the 

 resistance to the motion of any body are sensibly increased from the surface 

 to the bottom. At the depth of 3000 fathoms, for instance, the pressure 

 upon a square inch is nearly 8000 pounds: but the column of 18,000 feet of 



