Il8 CHALLENGER 



at a trying season of the year, of very continuous, and to them monotonous, 

 hard work over long hours each day and with little opportunity for recrea- 

 tion, with unfailing loyalty and response to all calls made for further efforts. 

 It is submitted to be particularly to the credit of each individual rating that 

 the work has no appeal in war-time when most of them desire more positive 

 and exciting service. 



Fixing the coastline can often be done in the way that has 

 already been described, that is by walking along the high water 

 line and fixing oneself at frequent and regular intervals by a 

 sextant and station pointer fix using three of the visible surveying 

 marks ; however, this cannot be done when a twist of the tree- 

 fringed coast cuts off the surveying marks from view, nor when 

 mapping inland roads, villages and jungle tracks. To do such 

 work 'traversing' is used, and there was much of this going on 

 during the surveying of the country on both banks of the Gambia 

 River, 



A traverse starts from a known position on the survey and 

 consists of a number of 'legs' at the end of each of which a peg 

 is driven into the ground. The direction of the first leg is found 

 by observing a reference angle at the starting point between it 

 and another mark in the survey, while the direction of each 

 subsequent leg is found by observing the angle between the leg 

 already traversed and that which lies ahead. The length of each 

 leg is also measured so that the positions of the pegs may be 

 plotted. This is done by the surveyor standing at one peg using 

 a theodolite to record the distance to a stave held by a seaman 

 over the next. Such a method is well knowoi to the surveyor, 

 being called 'tacheometry', while the curiously marked stave 

 which makes such measurement possible is known generally as 

 the 'tack' stave. 



Such a traverse can be progressed along winding roads or 

 tracks, the surveyor obtaining subsidiary bearings and distances 

 of features such as houses, conspicuous trees or streams, etc., so 

 that topography is built up along either side of the traverse. 

 Traverses eventually terminate on another of the main triangu- 

 lated marks of the survey, or even the original one from which 

 the traverse was begun. The less important topography such as 

 the remoter jungle tracks are traversed by measuring the legs 

 by pacing them out and finding their direction by pocket compass. 



