CHAPTER II 



A MARINE SURVEY IN GENERAL 



There is a great variety in the methods that can be em' 

 ployed in making a marine survey, so much so that the task of 

 describing any general scheme of operations is by no means easy. 



Under ordinary circumstances, it is often a good plan to 

 begin the survey of a coast from the shelter of some harbour, 

 of which it will eventually be necessary to make a plan on a 

 larger scale, and to extend the triangulation outwards from 

 thence. 



The base, which is measured primarily for the purpose of 

 the plan, being connected directly with the main triangulation 

 of the coast survey, is afterwards utilised for calculating the 

 long side upon Avhich we shall begin plotting the coast survey. 

 In case of the weather becoming unfavourable for the main 

 triangulation outside, a harbour plan to fall back upon prevents 

 the loss of time that might otherwise ensue under those cir- 

 cumstances ; this is specially the case when a large staff of 

 assistants has to be considered. 



In the survey of a particularly wild, stormy, and exposed 

 coast, such as the southern coast of Terra del Fuego, the general 

 plan adopted by Captain Fitzroy, of H.M.S. Beagle, was to 

 measure a base, and to survey, from the shelter of a harbour 

 fixed astronomically, as far afield as practicable, fixing points 

 to the utmost limit in every direction. Then, running for the 

 next harbour, a similar survey of it and the vicinity was 

 executed. The harbour surveys were afterwards connected by 

 sketch surveys, the ship being fixed on the points already 

 plotted, and all theodolite shots to intermediate points utiHsed 

 as far as practicable. The use of steam now enables this sort 

 of work to be carried out somewhat differently and more ex- 

 peditiously. 



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