OF THE. UNITED STATES. 395 



the sea will be determined by the vertical angles observed at 

 the stations. 



'I licsc additions to tlie mere hori'/.ontal survey will add 

 more interest and nsct'ulness to the work than ini!j;ht l)c ex- 

 pected, not only in a scientific point of view, but also for 

 public utility. Joined to an accurate aiul minute detail sur- 

 vey, executed u|)on the princijjles whicli will be exposed 

 heieafter, all the data slioidd be collected, to enable the go- 

 verninent to judge with piopiiety of the plan of any pulilic 

 imdertaking or service, such as roads, canals, means of de- 

 fence of the country. tS'c. That the survey of the coast was 

 to contain all these data, besides the mere outlines of the 

 coast, and that they were as necessary as the soundinj;s out- 

 side of the line of the coast, appeared to me too evident to 

 admit of any doubt, and I would have considered tiic full 

 aim of the work missed without them. 



Another addition, particularly useful to navigation, was to 

 obtain a comjilete series of observations of the variation of 

 the magnetic needle over tlie whole extent of the coast. 



I intended that the magnetic l)earings siiould be ol)scrved 

 at all the stations every day by an assistant, the needle being 

 stationary in one point for that purpose : I)ut during the shr)rt 

 time that I worked, the multiplitity of niy otiicr occupations 

 and other circumstances hindered me from doing more than 

 just to observe it once myself at the close of each station. 



An oscillation needle, which I have, and which lias been 

 observed in I'aris, in Lotulon, and in Washington, was in- 

 tended to be oI)served also regularly at each station. The 

 union of these two kinds of observation would have given 

 an interesting result relative to this sulijcct. 



It will not be necessary to enter into the reasons which 

 dictated the estal)lishment of one or more observatories con- 

 necied with the chain of triangles, then-by to bind the wink 

 to one or more permanent points astronomically determined. 

 The advantage of such an arrangement is perfectly evident. 



The following is the most proper orflerof the operations 

 on a favourable day, at any station. Every day's work nuist 



