30* SURVEY OP THE COAST 



serving, by an accuracy in the final results never obtained 

 without it. 



1 must here observe, in relation to the actual application 

 of this method of observing in my triangulation for the sur- 

 vey of the coast, that it will not be found to have been ri- 

 gorously followed ; because it was the result rather than the 

 element of that part of the work which I could execute. 

 The necessity of advancing in the work, at the same time 

 that I was bringing my method of observing to perfection 

 both by theoretical researches and by practice, caused me to 

 make use of all the observations obtained lor both purposes. 



In the examples of the Day-Book and the Journal of Re- 

 sults inserted at the end of the paper will be seen some fully 

 registered in proper order. These are taken from the work 

 on the Boundary Line with Canada, as I had not the oppor- 

 tunity of referring to any of my journals from the survey, 

 having delivered them to the War Department. 



The observations of the azimuths of celestial iiodies, par- 

 ticularly of the sun, are very accurate and easy with this in- 

 strument. They should unite in one final result a complete 

 system of the above compensating method of observing, be- 

 sides an equal number of observations made six hours before 

 and after the transit of the heavenly body used. This com- 

 bination is necessary in order to render the elements for the 

 calculations of the azimuths compensating to each other, and 

 the influence of their error the smallest possible, as well 

 as to make the observations the most favourable and accu- 

 rate. 



A full result of azimuths must therefore consist of twelve 

 observations, which is not more than the number whicli would 

 of choice be given to this element of the triangulation. With 

 respect to the instrument, it will be the mean of thirty-six 

 angles symmetrically situated upon the circle ; so that the 

 accuracy thus obtained must prove very satisfactory. In 

 case that this complete series of observations cannot be ob- 

 tained on a station, the only correction whicii may be omit- 

 ted is that of the change of the theodolite upon its legs. All 



