APPLICATION OF ELECTRIC TELEGRAPH. 305 



In the year 1845, a plan was adopted by Professor A. 



D. Bache, Superintendent of the Coast Survey, to apply 

 this method in an improved form, to the determination 

 of the difference of longitude between the principal sta- 

 tions of the survey ; and in 1846 measures were taken to 

 connect in this manner Washington, Philadelphia, and 

 New York. An arrangement was made with the tele- 

 graph company, to allow the use of their line for scien- 

 tific purposes, after the usual business operations had 

 closed for the day. A line of wires was extended from 

 the General Post Office in Washington to the Naval ob- 

 servatory ; a wire was carried from the main line through 

 the High School observatory at Philadelphia ; and a short 

 wire was carried from the office in Jersey City to a station 

 fitted up as a temporary observatory, and furnished with 

 a five-feet transit telescope and an astronomical clock. 

 The observations at Washington were made by Professor 



E. Keith ; those at Philadelphia by Professor E. O. Ken- 

 dall ; and those at Jersey City by Professor E. Loomis ; 

 the whole being under the direction of Mr. S. C. Walker. 

 Each station was furnished with a telegraph key and a 

 receiving magnet. 



Washington, Philadelphia, and Jersey City were thus 

 put in telegraphic connection ; instruments for obtaining 

 time were provided ; and to determine the difference of 

 longitude of the stations, required simply the means of 

 producing an instantaneous effect observable at all the 

 stations. This was to be obtained by the motion of 

 the armatures of electro-magnets, which had been pre- 



