THE TRANSATLANTIC LONGITUDE. 81 



1866, October 25, O'.SU Cable of 1866, with earth and condenser. 



28, .343 ' 



November 5, .280 Both cables, no earth. 



6, .248 " " " " 



9, 0.240 " " " " 



The battery-strength on these nights was as follows : — 



October 25, 10 cells at Valencia, 10 cells at Newfoundland. 



28, 10 " " " 10 " " " 



November 5, 8 " " " 3 " " " 



6, 3 " " " 10 " " 



9, 4 " " " 10 " " 



It was my intention that the battery 'employed at Newfoundland should in every 

 case be of equal strength with that used at Valencia ; but, through misapprehension 

 on the part of the observer at Heart's Content, this was not the case on either of 

 the last two of the five nights of our longitude-exchanges. Yet from the results 

 just given, the inferences seem warrantable, 1st, that the velocity of transmission is 

 greater when the circuit is direct and consists of a good metallic conductor exclu- 

 sively, than when the signals are given by induction, although the earth may be at 

 the other electrode ; and 2d, that an increase of intensity in the electromotive force 

 is attended by an increase in the velocity of propagation of the signal. 



From the beginning it was part of my design to arrange and make a system of 

 experiments for obtaining general answers, so far as might be possible, to sundry 

 interesting questions to which previous investigations had afibrded no satisfactory 

 replies. Among these were — 



1. The character of the agency which gives the telegraphic signal upon the 

 closing or interruption of the galvanic circuit, and the route by which its trans- 

 mission is effected. 



2. The influence exerted upon the conductor by using the earth as part of the 

 circuit, or by placing the complete circuit in electrical communication with the 

 earth. 



3. The extent to which the velocity of propagation of the signals is dependent 

 upon the intensity of the electromotive force and upon the resistance of the con- 

 ductor. 



4. The equality or difference in speed of the signals from the positive and from 

 the negative electrode, when the other is connected with the earth ; as also the 

 relative velocity of signals given by completing and by interrupting the circuit. 



Of course it was not to be expected that satisfactory information cculd be obtained, 

 or crucial experiments devised regarding aU these points ; but these were the guid- 

 ing ideas in providing for the additional experiments, which were carried out with 

 the friendly aid of the gentlemen of the telegraphic staff on the 1st, 10th, and 16th 

 of November. 



The length of the cable of 1865 is 1896.5 nautical or 2186 statute miles, and 

 that of the cable of 1866 is 1851.6 nautical or 2134 statute miles. Expressed in 

 metric units, the cable of 1865 is 3518 kilometers, and that of 1866 is 3435 kilo- 

 meters long. 



11 August, 1869. 



