122 ANNUAL OF SCIENTIFIC DISCOVERY. 



mended increasing it, as by that means a smaller battery was requisite. In 

 telegraphs by this method to Ireland or France, abundance of lateral distance* 

 could be got; but for America the lateral distance in Britain was much less 

 than the distance across. In the greater part of his experiments the distance 

 at the side had been double the distance across; but in the experiment across 

 the Tay the lateral distance was the smaller, being only about half a mile, 

 while the distance across was three-quarters of a mile. Of the four elements 

 above mentioned, he thought that if any one were doubled, the quantity of 

 electricity that crossed would also be doubled; and if all the elements were 

 doubled, the quantity transmitted would be eight times as great. In the ex- 

 periment across the Tay the battery-power was of four square feet of zinc; 

 the immersed sheets contained about ninety square feet; the weight of the 

 copper coil was about six pounds; the lateral distance was less than the 

 transverse distance, but if it had been a mile, and the distance across also a 

 mile, the signal would no doubt have been equally distinct. Should the 

 above law (when the lateral distance is equal to the transverse) be found cor- 

 rect, the following table might thus be formed: 



Zinc for battery. Immersed sheets. Coil. Distance crossed. 



Square feet. Square feet. Pounds. Miles. 



4 90 6 1 



8 180 12 8 



16 360 24 64 



32 720 48 512 



64 1440 96 4096 



128 2880 192 32,768 



But supposing the lateral distance to be only half the transverse, then the 

 distance crossed might be sixteen thousand miles; and if it was only a fourth, 

 then there would be eight thousand miles, and thus a greater distance than 

 the breadth of the Atlantic. Further experiments were, however, necessary to 

 determine the law. On the battery side he had made the electricity pass through 

 a coil of thick wire, and on the receiving side through one of small wire; 

 and when a battery and receiver were on each side, by means of a shifter of 

 communication, the path for sending was through the thick wire, and for 

 receiving through the small. Since this last experiment he had increased 

 the coil, and thought there was power to transmit signals for two miles. 

 According to this calculation, he thought a battery of one hundred and thirty 

 square feet, immersed sheets of three thousand square feet, a coil of two 

 hundred pounds weight, were sufficient to cross the Atlantic, with the lateral 

 distance that could be obtained in Great Britain. 



In the course of the discussion Sir D. Brewster said that he was a member 

 of the committee entrusted with the experiments alluded to by Lord Rosse 

 during the Great Exhibition. The result was this : they sent messages across 

 the Serpentine in the usual way; the wire was then broken. With a gap of 

 six feet the messages still went, and when the distance was increased to six- 

 teen and twenty feet they still went. 



Experiments of Mr. Beardmore.^lv. S. Beardmore, a civil-engineer of 

 London, has recently published a pamphlet on the subject of the applicability 

 of terra-voltaism to submarine telegraphs, in which he gives an account of 

 some hopeful experiments made by him between Cromer and Heligoland, 

 through a line three hundred miles in length. He employed a simple terra- 

 voltaic apparatus, such as he seems convinced must ultimately be used for 



