118 Sea Log and Sounding Machine . 
But though the principle of the two machines is the 
same, their construction necessarily differs considerably, 
as will be perceived on reference to the plate. 
Fig . 4, represents the sounding machine, a is the 
sounding weight, containing a register, 1, 2, with two 
dials : the hand of the dial 1 makes one revolution when 
the weight has descended twenty fathoms, the other re- 
volves once when the descent amounts to five hundred fa- 
thoms. A rotator, &, similar to that attached to the log, 
communicates with the wheel work of the dials i, 2, by 
means of the rod c, on which there are three universal 
joints, 3, 4, and 5. This rod is supported during the de- 
scent of the weight, by the drop, d , at the end of which is 
a fork, 6, and a friction wheel, 7* 
When the machine is to be used, a sounding line is fas- 
tened to the ring, e; and one of the vanes of the rotator is 
slipped into the spring 8 : the rotator will then be in the 
position indicated by the dotted lines, x . The indices 
must be set at 0, and the cover or lid, /, be shut. The 
machine must then be projected perpendicularly into the 
sea. As soon as it reaches the surface, the resistance of 
the water forces the dotted rotator, x , out of the spring 8, 
and it assumes its perpendicular direction as represented 
by the rotator b . As the machine descends, it is evident 
the rotator will revolve, and its motion be communicated 
freely past the friction wheel 7j and the universal joint 5, 
to the wheel work of the dials 1, 2, and thus indicate the 
space passed through in fathoms. When the machine 
has arrived at the bottom, the rotator, as it is no longer 
buoyed up by the reaction of the water, will fall to the 
bottom, quitting the fork of the drop */, which will also 
fall from its horizontal position, and in its descent, by 
means of the locking rod 9, prevent the rotator from re- 
volving as the machine is drawn up. When at the hot- 
