4 HYDROGRAPHICAL SURVEYING 



In tlie earlier days of hydrography, surveys were made on 

 small scales, and covered large areas which were more or less 

 imperfectly examined. A regular system of triangulation 

 being generally inapplicable to such conditions, commanding 

 officers were constantly stimulated to exercise their ingenuity, 

 and the assistant surveyors became habituated to methods of 

 fixing their points which demanded closer study of the geo- 

 metrical problems involved than when dealing with work con- 

 ducted on more regular lines. 



There is not now the same incentive as formerly to improvise 

 methods, owing to the larger scales of modern surveys and the 

 necessity for that minute examination of the ground which 

 is usually associated with regular triangulation. 



Such procedure is not to be discouraged in its proper place, 

 but stress is laid upon irregular triangulation, because the latter 

 is sometimes neglected when it might have been used with great 

 advantage in the saving of time without impairing the value 

 of the results. 



Rigid accuracy must always be insisted upon ; but, as a 

 general rule, a degree of accuracy which aims beyond that 

 which is necessary to plot points with precision on the scale 

 on which the survey is carried out is waste of time. 



It should be a cardinal principle in scheming a triangula- 

 tion to avoid unnecessary multiplication of main stations ; 

 much time is often wasted in making stations that serve no 

 useful purpose, and this applies with greater force when 

 wooded hills or mountains difficult of access are concerned. 

 Of fixed points, and secondary stations on or near the coast, 

 there should be an ample number ; and every conspicuous 

 natural object should be accurately fixed. 



Success depends chiefly upon the skill exercised by the officer 

 in command in economising the time at his disposal, or on hie 

 judgment in evading the difficulties caused by contrary winds, 

 bad weather, strong tides, an inhospitable population, and the 

 natural features of the coast ; and upon the concentrated 

 attention given by himself and his assistants to a multitude 

 of small details. 



The following pages will not be found to provide for every 

 occasion, but will describe the ordinary and accepted modes 

 of setting about work, giving examples of special cases illus- 

 trating difficulties that may be met with. 



