62 ANNUAL OF SCIENTIFIC DISCOVERY. 



at no very great depth, even when the line used is the smallest that will sus- 

 tain the weight with safety in the air; and in confirmation of this conclusion, 

 the fact is well established, that, notwithstanding repeated experiments, made 

 by the most skilful officers, and with the utmost care, the bottom of the 

 ocean has never been reached in its deepest parts ; and even where the bot- 

 tom has been attained, and specimens brought to the surface, the uncertain- 

 ties of the results have given good grounds for controversy with regard to 

 the depth. 



These failures and uncertainties do not arise from the magnitude of the 

 distance to be measured, nor from the impenetrability of the fluid through 

 which the lead has to pass; distances infinitely great and infinitely small in 

 the universe above and around us, have been measured with precision ; and 

 the unexplored depths of the ocean are occupied by a medium freely and 

 equally penetrable at all depths. Yet in this field afield daily traversed 

 by the commerce of the world a distance of a few miles only has baffled 

 all attempts to measure it. 



The difficulty lies in the simple cause stated above, viz., the "endwise 

 resistance" or friction upon the sounding-line, which prevents the lead from 

 going to the bottom where the depth is great. The apparatus now devised 

 is designed to avoid this friction upon the line, while at the same time the 

 line is not dispensed with, but is made use of, as in the ordinary mode. 

 Experiments have demonstrated, that an iron globe or sphere, when falling 

 freely on the ocean, will attain a maximum velocity, within twenty-five feet 

 of the surface, which will be kept up, without sensible increase or diminu- 

 tion, to the bottom. For a thirty-two-pound iron shot, this uniform velocity 

 is about sixteen feet per second. When attached, however, to a small line, 

 this line being uncoiled from a reel on the deck of the vessel, and drawn 

 down by the weight of the sphere, the friction of the water on the line 

 causes a remarkable change in the rate of descent. Nearly the same maxi- 

 mum velocity at starting is attained; but the velocity becomes rapidly re- 

 duced, until the sphere becomes suspended nearly motionless in the water. 



Taking the simple case of a thirty-two-pound shot attached to a small fish- 

 ing-line : the shot attains its maximum velocity of sixteen feet per second 

 within twenty-five feet of the surface; but before a hundred fathoms of the 

 line is drawn into the water, this velocity is reduced to eight feet per second 

 a diminution of half the velocity, from the friction of one hundred fathoms 

 of line. At five hundred fathoms, the velocity is again reduced half, or to 

 four feet per second; and at three thousand fathoms, to about one foot per 

 second. Whereas, at this depth, if there is no line attached, the shot will 

 fall with its original velocity of sixteen feet per second, undiminished. Be- 

 low this depth we may determine, in the same way, the circumstances in the 

 two cases ; the shot falling freely, still retains its uniform velocity of sixteen 

 feet per second, at four, five, and six thousand fathoms depth; while, with 

 the line attached, at five thousand fathoms, the velocity is reduced to a few 

 inches per second ; and at six thousand fathoms, the descent is not perceptible 

 under ordinary circumstances. 



The time of descent becomes an important element also in practice. In the 

 two cases given, the shot falling freely will descend to the depth of three 

 thousand fathoms in twenty minutes, and to the depth of six thousand 

 fathoms in forty minutes; while, with the line attached, it will require two 

 hours to descend three thousand fathoms, and eight hours to descend six 

 thousand fathoms. These effects have been proved to be due to the friction 



