352 HISTORY OF ASTKONOMY. 



time at the telegraph office in Berlin, upon a mean solar 

 chronometer, while Dr. Briinnow made similar observa- 

 tions upon a sidereal chronometer. The ten signals 

 being observed, Dr. Briinnow gave a signal from Berlin 

 to announce that a new set of experiments was about to 

 commence, and this was followed by ten successive sig- 

 nals as before. The following is the result for the lon<- 

 gitude of Frankfort west of Berlin : 



SIGNALS FROM FRANKFORT. 



August 12, 18m. 51-79s. Encke. 18m. 51-728. Briinnow. 



28, 61-718. 61-858. 



18m. 51-758. 18m. 51.79s. 



Mean 18m. 51'7 7s. 



SIGNALS FROM BERLIN. 



August 12, 18m. 51.57s. Encke. 18m. 51-92s. Brunnew. 

 28, 51-918. 5213s. 



18m. 61-748. 18m. 62'03s. 



Mean 18m. 51-89s. 



or on the whole, a mean difference of longitude amount- 

 ing to 18m. 51 '83s. The difference of the two results 

 can not arise from the circumstance that the transmission 

 of the signals is not instantaneous, since during the in- 

 terval of transmission, the Frankfort signals ought to 

 have arrived - too late at Berlin, in which case the differ- 

 ence of longitude should have turned out too great ; 

 while the Berlin signals by arriving too late at Frank- 

 fort should have indicated the difference of longitude too 

 small. In reality, however, the Berlin signals made the 

 west longitude greater than its true value. These experi- 

 ments consequently indicate that with the means of ob- 



