390 SURVEY OF THE COAST 



The chief observer, as well as all the assistants and the la- 

 bouring men, must be encamped at the station, the latter not 

 so close, as to occasion any impediment or interruption to 

 the observations by the noise of any other necessary occu- 

 pation. The living in neiglibouring houses is completely 

 incompatible with the advancement of the work. 



The safest, and at the same time most expeditious and 

 least expensive, mode of transporting the instruments is in 

 a spring carriage constructed purposely, the body of which 

 will closely fit the whole of the boxes of the instruments, so 

 that they stand in it packed, without being permitted to shake. 



On the first station of such a work, the task of tiie obser- 

 ver is of considerable extent, besides the mere observation 

 of the stations. He must begin by supposing his instruments 

 completely out of adjustment, which will certainly be the 

 case with all moveable instruments, particularly if they have 

 undergone any long transportation of any kind. He must 

 adjust them, and observe with them some time, not with the 

 view of the actual use of the observations in the work, but in 

 order to get acquainted with his instruments, to find an easy 

 mode of using them, and to discover all their qualities and 

 defects. 



Absolute mathematical accuracy exists only in tlie mind of 

 man. All practical applications are mere approximations, 

 more or less successful. And when all has been done that 

 science and art can unite in practice, the supposition of some 

 defects in the instruments will always be prudent. It be- 

 comes therefore the duty of an observer to combine and in- 

 vent, upon theoretical principles, methods of systematical ob- 

 servations, by which tlie influence of any error of his instru- 

 ments may be neutralised, either l)y direct means, or more 

 generally and much more easily by compensation. He must not 

 leave his first station, before he is so far clear upon this sub- 

 ject, as to need nothing more than the proof, always anxious- 

 ly looked for, of the sum of the three angles of Iiis lirst tri- 

 angles. It is not here the place to present a thi>ory on this 

 subject, nor to enter into practical details. I wdl merely re- 



