126 ANNUAL OF SCIENTIFIC DISCOVERY. 



VELOCITY OF ELECTRICITY. 



DR. B. A. GOULD, JR. read to the American Association, at New 

 Haven, and has since published in KiUinion's Journal for January, a 

 paper on the velocity of the galvanic current through the telegraph 

 wires. It is probably the most elaborate communication which has 

 appeared upon this interesting subject, containing some new views and 

 much that is interesting. Any attempt to give a complete abstract 

 would be impossible, and we must in a great measure confine ourselves 

 to the results arrived at. The experiments upon which they are 

 founded were mads on Feb. 4, under the direction of the officers of 

 the Coast Survey, on a line 1,045 miles in length, extending from 

 Washington to St. Louis, with stations at Pittsburg, Cincinnati, and 

 Louisville. 



After glancing at the history of this question and the various experi- 

 ments and views of Walker, Mitchel, Fizeau, and others, the author 

 goes on to give a detailed and popular account of the whole mode of 

 operation in determining this interesting, but difficult question, ex- 

 plaining the different sources of error and the means of obviating or 

 eliminating them as far as possible. Disputed points in the theory of 

 the electric action in these cases are discussed, and arguments brought 

 forward on one side and the other. The questions upon which the 

 most stress is laid are, 1st. Whether the stations on the line re- 

 ceived the signal pauses successively in their order of distance, and 

 after intervals directly proportionate to their distance from the place 

 where the signal was made. Dr. Gould says, " We are justified in 

 assuming that the signals given by making and breaking the galvanic 

 circuit of the telegraph reach the several stations successively in their 

 order of distance, and travelling with a finite and measurable velocity." 

 2d. Whether we are to consider, when the two distant extremities 

 of a line of wire communicate with the earth at a distance of many 

 hundred miles from one another, that there is a special line of tension 

 through the earth from one extremity to the other, and that a signal 

 is communicated from terminus to terminus through the ground, in 

 the same manner as it is through the wire, or may we consider the 

 earth as a huge receptacle, to speak metaphorically, capable of receiv- 

 ing or imparting any amount of electricity at any time? The author 

 sums up the argument on both sides, and says, " From all these con- 

 siderations I infer that in the St. Louis and Washington experiments 

 for velocity, which were, of all that have been made, the most favor- 

 able for exhibiting the phenomena, the signals were in no case trans- 

 mitted through the ground." 



The general conclusion of the whole paper is as follows: " Our 

 results, obtained from different data, accord so well with one another, 

 as to make it appear very improbable that the velocity of the propaga- 

 tion of the electric state produced in the telegraph wires by a galvanic 

 battery is more than 20,000 or less than 12,000 miles per second." 

 By taking the mean of the results of all the experiments made by the 

 Coast Survey, 15,890 miles per second is the velocity obtained. 



Wheatstonc, it will be remembered, obtained some years since a 



