TELEGRAPHING WITHOLT WIRES. 441 



increased battery power; Second — by increasing the surface of the immersed 

 sheet; Third — by increasing the coil that moves the receiving needle ; and Fourth 

 ■ — by increasing the lateral distance. In cases where lateral distance could be 

 got he recommended increasing it, as by that means a smaller battery was re- 

 quisite. In telegraphing 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 experiments 

 in 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 elec- 

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

 the quantity transmitted would be eight times as great. In the experiment across 

 the Tay the battery was of four square feet of zinc, the immersed sheets con- 

 tained 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 correct, the undermentioned table might then be 

 formed. 



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

 distance cr6ssed might be 16,000 miles, and if it was only a fourth, then there 

 would be 8,000 miles, and thus a greater distance than the breadth of the Atlan- 

 tic. Further experiments were, however, necessary to determine the law. Since 

 last experiment he had increased the coil, and thought there was power to come 

 two miles. According to this calculation, he thought a battery of 130 square 

 feet, immersed sheets of 3,000 square feet, a coil of 200 pounds weight were suf- 

 ficient to cross the Atlantic with the lateral distance that could be obtained in 

 Great Britain." 



The following is the table above referred to : 



If Mr. Lindsay's hopes are to be realized, some great discovery yet remains 

 to be made, for, by the laying of the Atlantic telegraph cables, we know that the 

 electric current, transmitted across the wide expanse of the Atlantic, must be of 

 extraordinary power to be apparent on the other side, even with a cable to lead it. 

 Without a cable it would be hopeless to expect to find it, although the best apparatus 

 were employed. Telegraphic instruments are greatly improved since Mr. Lind- 



