442 



HYDROGRAPHICAL SURVEYING [chap xx. 



at which the sweep is set can be seen from the following table, 

 which is applicable to the old pattern red kite of James sub- 

 marine sentry (see Fig. 100), and used with the particular 

 description of wire above stated. The dimensions of the kite 

 are given in Fis;. 100. 



Kite Wire Out. 



Depth of Sweep. 



6 fathoms 



8 „ 

 10 „ 

 12 



26 feet 

 34 ,, 

 4o „ 

 56 „ 



The general construction of the sweeping machines may be 

 seen by inspection of Figs. 98, 99. and 101; the framework, 

 plates, and drums being made of mild steel, the band brake 

 (b) and its adjusting gear of brass, and the brake drum (en- 

 closed between the two j)lates a' and a) of wood. 



Fig. 100. 



Secure Sweep Wire here 



The kites will carry the 50 yard wire sweep and still remain 

 exactly astern of these respective boats at any speed between 

 3 and 6 knots : the distance line and wire sweep being of equal 

 length, if the former is taut, the sweep will be taut also. 



