THE CABLE SHIP ON REPAIRS. 



191 



ments were with long fibres ; but soon after the completion of 

 the 1866 Atlantic cable, Mr. Graves, the superintendent at 

 Valentia station, together with Mr. T. E. Weatherall, carried 

 out a series of experiments starting with fibres 2in. long each 

 side of the mirror, and found that as they reduced the length 

 of fibre step by step the Instrument continued to retain its 



sensitiveness until a length 

 of only y'ein. was found to 

 be necessary for good sharp 

 signals. 



The Mark Buoy.— The ship 

 generally manages to reach 

 the position of the fault some 

 time in the morning, so as to 

 get an altitude for the longi- 

 tude of the position. A sound- 

 ing is also taken, and the lati- 

 tude is ascertained at noon. A 

 steel mark buoy, such as shown 

 in Fig. 98, and weighing about 



Fig. 98.— The Mark Buoy. 



Fig. 99.— The Mushroom Anchor. 



18 cwt., is then moored as nearly as possible over the position- 

 of the cable to act as a guide while grappling, and as a bearing 

 to go by when the cable is hooked. The buoy is moored by 

 means of a 3 cwt. mushroom anchor (Fig. 99), this particular 

 form of anchor having been found to hold well in almost any 



