SURVEYING THE ROUTE. 



31 



the tow line being attached to a spar (S) outrigged at the fore 

 part of the ship and projecting about 20 feet over the side. 

 The torsion line (t) connected to the tail of the log communi- 

 cates the rotation to the indicator on the bridge. This position 



Fig. 22. — TrafFrail Indicator and Governor. 



is an extremely handy one, all readings being taken on the 

 bridge instead of calling the quartermaster and sending him 

 aft to read the indicator. Further, the rotator is in full view. 



Fig. 23. — Captain Thomson's Log. 



and if not working properly from any cause is at once seen 

 and put right. 



The depth of the log in the water is regulated by means of 

 a chain and bearing line. The short length of chain inserted 



