XVI. 



On the Determination of Transatlantic Longitudes by Means of the Telegraphic Cable*. 



LLE 



by permission of Professor Benjamin Peirce, Superintendent of 



U. S. Coast Survey. 



After the Telegraphic Cable had been successfully laid between Trinity Bay in 

 Newfoundland and Valencia in Ireland, no time was lost by the Superintendent of the 

 U. S. Coast Survey in making it available for the determination of differences of 

 longitude between the principal meridians of the British Islands and the principal 

 meridians of the United States. The processes and the results of tins operation have 

 been fully and* ably explained in other publications. 1 In the winter of 18G9-70, 

 advantage was taken of the French cable, which was then open between Dux bury, 

 Mass., and Brest, France, by the way of the island of St. Pierre, near Newfoundland, 

 to connect, by time-signals, Brest with Duxbury and Duxbury with Cambridge, 

 and hence with Washington. Again, in the summer of 1872, Cambridge exchanged 



time-signals with St. Pierre by another route, and St. Pierre exchanged signals with 

 Brest by the French cable. Moreover, Mr. J. K Hilgard, of the U. S. Coast Survey, 

 was despatched to Europe to superintend the exchange of time-signals between Brest 

 and Paris, and between Paris and Greenwich. When all the computations which are 

 required for deducing the final result from the work of the last summer are finished, 

 the Coast Survey Office will possess three independent determinations, by the tele- 

 graphic method, of the difference of longitude between Greenwich and Washington. 

 The comparison which has already been made, by anticipation, between the deter- 

 minations which have been thoroughly computed and those which, as yet, are only 

 known approximately, justifies the expectation that, when the labor of the computers 

 is finished, all the different results will correspond to a surprising degree. The 

 present communication is limited to giving some details in regard to the campaign of 

 1869 - 70, and the subsequent calculations which grew out of it 

 The astronomical station occupied by the U. S. Coast Survey at Brest was under 



1 Smithsonian Contribution tc 

 VOL. IX. 61 



XLIX 



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