59 6 The Smithsonian Institution 



nomical observations of the former expedition made by 

 Doctor Emil Bessels, were all reduced in Washington. 



TRANSATLANTIC LONGITUDE 



THE determination of longitude x by telegraph was, as is well 

 known, first practised by American astronomers. The differ- 

 ence of longitude between Baltimore and Washington was 

 fixed, in 1844, by Captain Wilkes, who compared his chro- 

 nometer at Baltimore with signals received from Washington. 

 Professor Sears C. Walker in 1845, an ^ subsequently, put the 

 telegraphic methods into practical form, and they were soon 

 adopted as the work of a regular department of the Coast 

 Survey, with the cordial support of Professor A. D. Bache, 

 the Superintendent. Professor Loomis was a coadjutor of 

 Walker in this work ; and subsequently the longitude ser- 

 vice of the Survey was under the direction of Doctor B. A. 

 Gould, who improved it in many respects. By the efforts of 

 these astronomers, aided by the chronographs lately invented 

 by Bond and Mitchel, and by devices due to Saxton and 

 others, the methods of observation were brought to a high 

 degree of accuracy. The observations themselves were re- 

 duced by rigorous methods. 



From 1846 to 1861, the date of the beginning of the Civil 

 War, the telegraphic determinations of longitude had followed 

 the extension of the commercial lines of wire until, in the lat- 

 ter year, they extended from the northeastern boundary of 

 the United States to New Orleans, covering 2^/2 hours of 

 longitude and 15 of latitude. The problem of the connec- 

 tion of American with European longitude was on a different 

 footing. Until the Atlantic cable was available the ocean lon- 



1 Gould, Benjamin A., "The Transatlantic published in 1869 and forms the sixth paper 

 Longitude as determined by the Coast Sur- in Volume xvi of the " Smithsonian Contri- 

 vey Expedition of 1866." This memoir was butions to Knowledge." 



