ON THE 



TRANSATLANTIC LONGITUDE. 



ORIGIN Of THE COAST-SURVEY EXPEDITION. 



The determination of longitudes by means of the electro-magnetic telegraph, 

 was, as is well known, first practised by the U. S. Coast Survey ; and the methods 

 by which it attained its full development were here in use for several years before 

 they began to be employed elsewhere. From the year 1849 until the beginning 

 of the late war, early in 1861, they were unremittingly prosecuted. At that time, 

 24^ndependent determinations had been made, no pains having been spared for the 

 attainment of all possible precision ; and the series of telegraphic longitudes ex- 

 tended from the northeastern boundary to New Orleans, covering 2| hours of 

 longitude and 15° of latitude within our own territory, as well as some portions of 

 the British provinces. Upon the completion of the Pacific Telegraph, arrange- 

 ments were made^ for extending the connection to San Francisco ; but these were 

 reluctantly deferred in consequence of the condition of the country. 



For longitudes reckoned from any trans- Atlantic zero, much coarser methods only 

 have hitherto been available ; and the uncertainty of the determinations has been 

 twenty or thirty times greater than that between any of the points which form the 

 series of American determinations, and very much larger than that between any 

 points referred to these fundamental ones, by the geodetic operations of the 

 Survey. 



The Atlantic cable promised at last to afford an opportunity of connecting the 

 American with the European longitudes, and thus of reducing the two independent 

 series of determinations into what should practically be but one. The large views 

 of the late honored head of the Coast Survey, Prof Bache, led him to take imme- 

 diate steps for the attainment of this end ; and upon the first organization of the 

 Atlantic Telegraph Company, to the assistance of which he gave his hearty and 

 eftective support, he obtained^ from the ofiicers of this and of the Newfoundland 



^ Coast Survey Report, 1861, p. 2. 



" Ibid. 1858, pp. 33, 34, 43 ; 1859, p. 6. 



1 April, 1869. r 1 "^ 



