W. P. Trowbridge on a new Sounding Apparatus. 3 
being uncoiled from a reel on the deck of the vessel, and drawn 
down by the weight of the sphere. The friction of this line in 
the water causes a remarkable change in the rate of descent. 
Nearly the same maximum velocity at starting is attained, but 
the velocity becomes rapidly reduced, until the sphere becomes 
suspended nearly motionless in the water. 
aking the simple case of a 82 lb. shot attached to a small 
fishing line, the shot attains its maximum velocity of sixteen feet 
isa second within twenty-five feet of the surface, but before a 
undred fathoms of the line is drawn into the water, this ve- 
ne foot per . Whereas at this depth, af there is no line 
attached, the shot will fall with its orijinal velocity of sixteen feet per 
second undiminished. ow this depth we may determine, in 
the same way, the circumstances in the two cases: the shot fall- 
ing freely still retains its uniform velocity of sixteen feet 
second at four, five, and six thousand fathoms depth, while with 
the line attached, at five thousand fathoms the velocity is redu 
to a few inches per second, and at six thousand fathoms the de- 
friction alone; the amount of which in pounds, was determined 
for different cases, in which different forms of weight and differ- 
ent sizes of lines were used; and the entire inapplicability of 
the ordinary mode of sounding for great depths, and even for 
ordinary depths, where the object is to obtain a correct knowl- 
edge of the depths, was demonstrated. 
Methods have been proposed in which a line is dispensed 
with, by detaching a float at the bottom, when the plummet 
strikes, and watching for the return of the float to the surface;” 
but this is impracticable, as there is no material applicable, 
within our knowledge, that will float to the surface from the 
ttom of the sea, on account of the great pressure, which con- 
denses the bulk, so us to render bodies specifically lighter than 
= at the surface, heavier than water at even moderate 
A line must therefore be used to bring back to the surface any: 
machine by which the depth may be registered in the descent. 
