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Sea Log and Sounding Machine . 
taming the true perpendicular, and the uncertainty as to 
the exact moment when the lead strikes the bottom, upon 
which the accuracy of the result depends, must always 
prevent the possibility of obtaining the true depth, while 
the ship has any considerable way upon her. Indeed, it 
has been acknowledged by experienced seamen, during 
some experiments, made at various times, in the river 
Mersey, that they could not depend upon the common 
lead, when going five or six knots in the hour, in ten or 
twelve fathoms of water. When the depth is considera- 
ble, the vessel must be hove to, which is an operation at- 
tended with great loss of time, and sometimes considera- 
ble injury to the sails ; and during a chase, this inconve- 
nience must be particularly felt. 
Massey’s sounding machine is as great an improvement 
upon the common lead, as his patent log is upon the com- 
mon log. A rotator on the same principle as that to the 
log registers the perpendicular descent of the lead, with- 
out any respect to the length of line paid out, which, in 
the usual method of taking soundings, is the chief guide 
to the mariner in judging of the perpendicular depth, and 
is apt to deceive him much. 
True soundings may be taken with this machine in 
thirty fathoms water, without the trouble of heaving the 
vessel to, although she may be going at the rate of six 
miles in the hour. True soundings may also thus be ob- 
tained in very deep water, where it is not possible to take 
them by the common lead. 
This sounding machine is on the same principle as the 
log, for it is evident, that, if the end e of the register, a 9 
(jig. 3,) were projected into the water, and suffered to 
descend, the rotator would follow r , and register the exact 
depth, as well in a perpendicular, as in a horizontal posi- 
tion. 
