APPLICATION OF THE ELECTKIC TELEGKAPH. 311 



his telescope upon one of the selected stars as it is 

 passing his meridian, and strikes the key of his register 

 at the instant the star appears to coincide with the first 

 wire of his transit. He makes a record of the time by 

 his own chronometer; and the New York astronomer, 

 hearing the click of his magnet, records the time by his 

 own clock. As the star passes over the second wire of 

 the transit instrument, the Cambridge astronomer again 

 strikes the key of his register, and the time is recorded 

 both at Cambridge and New York. The same operation 

 is repeated for each of the other wires. The Cambridge 

 astronomer now points his telescope upon the next star 

 of the list, which culminates after an interval of five 01 

 six minutes, and telegraphs its transit in the same man- 

 ner. In about twelve minutes from the former observa- 

 tion, the first star passes the meridian of New York, when 

 the New York astronomer points his transit instrument 

 upon the same star, and strikes the key of his register 

 at the instant the star passes each wire of his transit. 

 The times are recorded both at New York and Cam- 

 bridge. The second star is telegraphed in a similar 

 manner. The Cambridge astronomer now selects a 

 second pair of stars, and repeats the same series of opera- 

 tions, and is followed by the astronomer at New York, 

 when the star comes upon his own meridian. By this 

 comparison, the difference of time between the two 

 stations is obtained independently of the tabular places 

 of the stars. 

 On seven nights in July and August these methods 



