DESCRIPTION OF THE MODE OF SOUNDING . 43 
worthy results can be obtained from a ship under 
sail, as even in the calmest weather the heave of the 
sea, or the surface current, is sufficient to drift the 
ship in a very short time a considerable distance from 
the place where the lead was originally let go. It is 
thus impossible to obtain a perpendicular sounding ; 
besides the time intervals between the 100-fathom 
marks are upset, these time intervals being the only 
means of telling when the lead has reached the bottom. 
The first thing, therefore, to be done is to shorten 
and furl all sail, and bring the ship head to wind, 
regulating the speed in such a manner as to avoid 
forcing her through the water. 
The sounding apparatus is then got ready. A 
block is placed on the main-yard a 
little outside the boom iron, and a 
whip rove through it to trice up the 
accumulator (Fig. 1). These accu- 
mulators are india-rubber bands, f inch 
in diameter and 3 feet in length. 
They are capable of stretching 17 feet, 
when they each exert a pressure of 
70 lbs. Twenty pairs of these accu- 
mulators have been found sufficient 
for most of the soundings obtained, as 
they are strong enough to withstand 
the strain of the weights on the lead line without 
being too strong to give readily with the motion 
of the ship ; their greatest use being to keep the 
