APPLICATION OP THE ELECTRIC TELEGRAPH. 351 



On May 25, 1853, signals were passed in the same 

 manner to and from Edinburg, for the determination of 

 the longitude of Edinburg observatory. In these com- 

 parisons the following result was obtained, that when a 

 signal is given at Greenwich by means of a Greenwich 

 battery, the time noted for the signal at Edinburg is later 

 than that noted at Greenwich by T * T of a second of time, 

 and vice versa, if the signal is given at Edinburg by means 

 of an Edinburg battery. This difference Professor 

 Airy ascribes to two causes ; first, the time actually oc- 

 cupied by the transmission of the galvanic pulse, which 

 according to the American determination, would explain 

 less than half of the difference ; secondly, the circum- 

 stance that the galvanic current when it reaches the 

 distant needle is somewhat less vigorous than when it 

 passes the nearer needle, and the languid movement of 

 the distant needle catches the eye more slowly and is re- 

 corded as occurring at a later time. 



In August, 1853, observations were made to determine 

 the difference of longitude between the observatory at 

 Berlin and that at Frankfort on the Maine. M. Encke 

 and Dr. Briinnow observed at the former station, and Dr. 

 Lorey at the latter. The telegraph apparatus employed 

 was Morse's. It was agreed that Dr. Lorey should an- 

 nounce by signal when the experiments were about to 

 commence, after which he was to make a series of signals 

 during the next ten minutes, it being arranged that he 

 was to make a new signal about the beginning of each 

 successive minute. M. Encke observed the corresponding 



