SURVEYS. 



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SURVEYS. 



The surveys made by the Expedition were numerous, amounting to 

 234, during the four years of our absence from the United States. It 

 will readily be seen, that in order to accomplish this amount of work, 

 that some expeditious method of surveying the numerous coral islands 

 had to be adopted ; indeed, it may almost seem incredible, situated so 

 far asunder as the surveys were, for even a much larger force than 

 was placed at my disposal to execute them ; but as the mode of con- 

 ducting them will be shown, I trust that all will be satisfied that it 

 was quite possible not only to execute the work, but to do it with ac- 

 curacy. 



In surveying operations it is all-important that an easy and per- 

 spicuous method should be adopted, as well in taking the observations 

 as in recording them, particularly where it would be impossible to 

 regain an opportunity that might, from inattention or neglect, be 

 suffered to escape ; and any one who may have the direction of such 

 duties, should be careful that the rough charts be at once drawn 

 from the note-books, and that these latter should be kept in so clear 

 a manner, and in a formula so well understood, as not to require 

 explanations. In order to effect this object, I deemed it necessary 

 that all the officers should have a thorough knowledge of the operations 

 by which I intended to carry on the surveying duties, and for this 

 purpose I prepared a short syllabus, to render them familiar with the 

 operations, and to avoid the defects existing in all treatises on sur- 

 veying that I have hitherto seen, which appear to me to omit the first 

 and most essential explanation of the principles. Many things appear 

 to be taken for granted which the learner does not know, nor where 

 to look for information, and he is consequently apt to neglect their 

 importance. In other words, he must acquire much practical experi- 

 ence before he can understand the performance of duties which they 

 pretend to teach. This omission is a serious one, and prevents the 

 works on surveying from being as useful as they ought to the learner. 



I gave (in Appendix xli, vol. i) the manner of executing our 

 surveys, by the squadron, under sail: it had not been practised before, 

 although the method of measuring bases by sound has been exten- 

 sively used. As it more properly belongs to this place, I shall tran- 



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