238 SCIENTIFIC RECORD FOR 1884. 



nights that the comparisons were made, by carefully observed transits 

 of standard stars. This chain consists of the transatlantic longitude 

 measurements of the United States Coast Survey from Greenwich to 

 Washington; a Coast Survey measurement from Washington to Key 

 West ; a measurement from Key West to Panama, by way of Havana 

 and Jamaica, by officers of the United States Navy, in 1874 and 1875 ; 

 from Panama to Valparaiso, as mentioned above ; from Valparaiso to 

 Buenos Ayres, by way of Cordova, under direction of Dr. B. A. Gould; 

 and from Buenos Ayres to Greenwich, by way of Rio de Janeiro, 

 Madeira, and Lisbon, by officers of the United States Navy,'tn 1878 and 

 1879. In closing this immense chain of twenty links or connected 

 measurements, the entire discrepancy amounted to eighteen one-hun- 

 dredths of a second of time. 

 The longitude of the Observatory of Cordova was found to be: 



Determined by way of Buenos Ayres 4'' 16™ 48". 06 



By way of Valparaiso 4 16 48 .24 



0.18 

 NORTH AMERICA. 



Among the scientific investigations and the geodetic, geographic, and 

 hydrographic work which marked the progress of the United States 

 Coast and Geodetic Survey during the past year, the following opera- 

 tions deserve special mention. 



In order to complete the connection of the American and European 

 initial gravity stations the observations needed were made at the Kew 

 and Geneva Observatories. 



A valuable series of comparative observations for gravity was com- 

 pleted at Washington with the Kater pendulums. These pendulums, of 

 historic importance in connection with determinations of gravity in 

 England and India, were swung at the station in the Smithsonian In- 

 stitution, where they had been previously swung by an officer of the 

 Royal Engineers. 



The work of tracing out and marking the boundary line between 

 Pennsylvania and West Virginia for the joint commission of these two 

 States was completed ; the resurveys of Long Island Sound and of 

 Delaware Bay were advanced toward completion, also the topograph- 

 ical survey of the District of Columbia, for the Commissioners of the 

 District ; lines of level of precision were begun to connect the tidal 

 levels of Chesapeake Bay and the Gulf of Mexico with the transcon- 

 tinental line of geodesic leveling ; progress was made in the primary 

 triangulation near the thirty-ninth parallel for connecting the triangula- 

 tion of the Atlantic coast with that of the Pacific; and trigonometrical 

 surveys were continued in nine States which made requisite provision 

 for their own topographical and geological surveys. 



Developments of much importance to the interests of commerce and 

 navigation were made during the year ; dangerous shoals and ledges 



