THE CABLE SHIP ON REPAIRS. 



2ia 



chairs, to put the chain or rope stoppers on each side oi the 

 cable. Instances have also occurred of cable being found 

 caught on the mushroom of the mark buoy, showing the 

 accuracy with which the first position has been determined. 



Dynamometers. — While grappling, the strain is indicated 

 on a dynamometer on board. One type of dynamometer in use 

 is shown in Fig. 124. The grapnel rope is taken on the under- 



FiG. 124. — Ship Dynamometer. 



side of a sheave or pulley on the apparatus, free to revolve as 

 the rope is paid out or picked up, and the rope is led down to 

 the sheave at an angle and up again the other side, so that any 

 strain on the rope tends to raise the sheave. For this purpose 

 the spindle of the sheave is fixed to a block of definite weight 

 free to move vertically between guides. When a strain comes 

 on, the rope tends to straighten out, so lifting the sheave and 

 block through a vertical distance varying with the strain. 

 The block carries a pointer indicating the strain on a vertical 



