12 THE TRANSATLANTIC LONGITUDE. 



Valencia ; then two sets returned from Heart's Content ; and this exchange will be made three 

 times, which will suffice for the telegraphic work of the night. The time requisite will therefore be 

 2m. 10s. for each series of two sets. Three such series being sent from each station, the time 

 actually consumed for the signals will be but 13m. ; so that 20m. will probably suffice for the whole 

 operation. 



c). Before sending each series of taps, the sender will call attention by a few rapid alternations 

 of positive and negative signals, to be answered in the same way before he begins the series; conse- 

 quently the order of proceedings will be as follows : — 



Valencia gives rapid signals, and Heart's Content responds. 



-n,- , t:, 1 Valencia sends two series of taps, occupying 2m. 10s. 



First Exchange. i > u a 



Heart's Content gives rapid signals, and Valencia responds. 



Heart's Content sends two series of taps, occupying 2m. 10s. 



Valencia then proceeds to give the preliminary signals for a second exchajjge, and in this way the 

 three exchanges are made. If possible, each observer should then state whether the signals have 

 been successfully received. 



5. The length of the taps, and of the intervals between them, is a matter of some importance. 

 Hence a mean-time watch or clock should be used, and the same care taken in giving signals as in 

 making observations. Especially should all the taps be of equal length. 



The observer of signals should have the break-circuit key of the chronograph in his hand, and 

 record the earliest indication of deflection. Should the deflection ever be in the reverse direction 

 of that indicated by the programme, this fact should be noted. 



6. It may conduce to a better determination of the time of transmission if exchanges are made at 

 different hours of the day. One " set" of ten taps as already described, exchanged at the beginning 

 of each third hour, would probably suffice for this purpose, although each alternate hour would be- 

 preferable. These experiments should be made on both cables separately, and, if possible, on the 

 circuit formed by connecting the two cables, without any earth-connection to either. The times for 

 these experiments must be left to subsequent arrangement. 



If possible, the following experiments for velocity should be made by use of both cables. They 

 are more important than the system of observations at different hours of the day. 



I. The two cables being connected at Heart's Content, but without battery there, Valencia first, 

 and then Heart's Content, will send two sets : — 



1. With the two ends to earth at Valencia through battery. 



2. With the two ends to earth at Valencia, one through battery, the other direct. 



3. With the two ends at Valencia to the two poles of battery without earth connection. 

 II. The same connection with the Heart's Content battery included in the circuit. 



III. (Like I., vice versa). The cables being connected at Valencia without battery ; Valencia 



first, and then Heart's Content will send two sets : — 



1. With both ends to earth at Heart's Content through battery. 



2. With both ends to earth at Heart's Content, one through battery, the other direct. 



IV. The same, with the Valencia battery included in the circuit. 



1. At the earliest convenient opportunity after an exchange of signals, each observer will com- 

 municate to the other his corrected sidereal time, corresponding to the means of the last set of ten 

 taps received, and the last set of ten taps sent. 



On the 24th October, longitude-signals were exchanged with Newfoundland for 

 the first time. Between that date and November 20, four more opportunities had 

 been found, and the entire series of experiments for determining the velocity of 

 signals under different circumstances had been satisfactorily tried, as well as some 

 others which I found practicable at Valencia, although not provided for in the 

 programme. 



Meanwhile the Astronomer Royal, who had, with his usual kindness, acceded to 



