i So 
THE TELEGRAPH . 
the line or cable. In order to keep the cable tight it is made 
to pass into the groove of another pulley of two feet diameter 
placed behind the drum. The cable on leaving the drum is 
pressed into the deep groove by means of a “jockey pulley" 
loaded by a weight. The grooved pulley is connected with 
the taking-up machine, and revolves with such a velocity as to 
keep always the proper degree of tension on the cable w T ound 
round the drum. A wrought or cast-iron guide is fixed against 
the drum where the cable goes upon it. This guide makes 
the cable pass properly round the drum, so that one turn is not 
superimposed upon the other, and the cable always enters upon 
a clear part of the drum. This' guide is adjustable, and is 
always case-hardened or faced with steel. 
Besides this machinery there is another grooved pulley 
behind, similar to the one in front, and provided with brakes 
for re-laying the cables. The machinery is merely the counter¬ 
part of the fore machinery, and fig. 103 will suffice to make it 
understood without further description. 
For short distances a method of under-running the cable has 
been used with advantage, as it can thus be brought to the 
surface of the water for examination. A tackle pulley about a 
yard in diameter (fig. 117) in a stout iron frame is hung over 
the front part of the ship away from the side. It can turn on 
a ring, and is kept in position by chains. After the cable to 
be examined has been raised by grapnels, it is passed through 
one side of the pulley-frame, which is made to open and shut 
for this purpose. It is therefore unnecessary to cut the cable. 
The ship can then, by steaming slowly, raise up the whole cable 
