62 CHALLENGER 



the angle between one of these fixed points, and a third, then 

 he knows that his position will lie at the point of intersection of 

 the two circles, the diameters of which are determined from the 

 angles which he has observed. 



To fix the coastline the surveyor walks along the shoreline, 

 stopping at each alteration of direction of the coast, when he 

 fixes his position by observing the horizontal angles between three 

 well-selected triangulation stations or secondary marks. He can 

 then plot his position with a pair of station pointers, an instru- 

 ment with three long metal arms, two of which can be moved 

 either side of the central fixed arm to set on the angles observed 

 by the sextant; and when the angles are set the station pointers 

 can be moved on the field-board until the three arms pass through 

 the three selected stations. The observer's position is then in- 

 dicated by a small V cut at the centre of the station pointer. 

 When a number of such fixes have been dotted, circled, and 

 numbered in pencil, they can be joined up rather as children 

 connect up numbered positions on a blank drawing featured in 

 children's papers and find they have drawn an ostrich or a boy 

 wheeling a barrow. The surveyor's less exciting picture will be 

 the coastline. 



It was a pleasant enough occupation to go for a day's coastlining 

 on an island in the Grenadines. Accompanied by a surveying 

 recorder companion, the surveyor walked the shoreline, the 

 turning of each small point of land opening up fascinating new 

 vistas — a yellow, sandy, palm-fringed beach; a rocky cove with 

 sparkling blue water heaving towards the rocks; the long thin 

 white line of breakers on the windward side of the pale green 

 reef; a hutted village beneath the trees. From such huts came the 

 smiling people to see what strange 'looking' and writing was 

 going on as the surveyor sketched in his field book the details of 

 the shore or the trees and huts behind. The children followed 

 for a mile or so and felt well rewarded when allowed to peer 

 through the telescope of the sextant, through which they probably 

 saw nothing. A halt for a sandwich lunch in a cool palm grove, 

 a bathe, and then on and on along the shore the coastliners went 

 until the boat came in through the surf to collect them and take 

 them back to the ship; onboard the weary pair would plot and 

 ink in the day's work and feel, over an iced whisky or a tot of 



