PRELIMINARY 3 



We write mainly for those who join the Surveying Service, 

 and shall speak throughout as though we had the resources of 

 an ordinarily fitted surveying ship at command. 



We have endeavoured to take things in the order that they 

 will generally come in the prosecution of a survey. 



In work of the nature of Hydrographical Surveying, it is 

 impossible to give directions as to how to undertake every 

 detail. Ordinary means fail now and again from exceptional, 

 local, or other circumstances, and ready resource in over- 

 coming difficulties is one of the most important requisites in a 

 nautical surveyor. To invent or improvise a method of doing 

 a particular piece of work is a most satisfactory achievement 

 when successful, but it is scarcely necessary to say that this 

 can only come to the most naturally talented with experience. 



The conditions under which modern surveys are usually 

 carried on tend to confine the experience of many surveying 

 officers to regular triangulation ; this is apt to engender a 

 certain want of resource when difficulties arise in the course of 

 a survey requiring other methods. 



The fact of being unaccustomed to irregular triangulation 

 involving the use of the ship, produces a distrust of such 

 methods arising from an imperfect realisation of the accuracy 

 of the results obtainable therefrom. 



This leads to a tendency to neglect the study of such means 

 and their application to cases which not infrequently arise. 



A considerable number of examples of irregular triangula- 

 tion have been inserted in the present edition, for the purpose 

 of giving to officers whose experience has been obtained in 

 other directions some foundations upon which to build. 



These examples, being based on practical experience, are 

 illustrative of conditions occasionally to be met with. They 

 do not pretend to be exhaustive, but it is hoped they may be 

 helpful in suggesting various ways of overcoming difficulties. 



Much time and unnecessary labour may often be saved by 

 the judicious use of the ship. Recourse to regular triangula- 

 tion in wooded country involves the occupation of numerous 

 shore stations, and the attendant labour and loss of time in 

 cutting timber, which might possibly be avoided by an intelli- 

 gent appreciation of what is possible by looking at the problem 

 from other points of view. 



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