1839.] Telegraphic Signals by induced electricity. 729 



§ 6. — Water a conductor of "Pulsation Signals. 



During the preceding series of experiments, I had ample proof 

 of the great conducting power of water for this form of electrical 

 impulse. Shocks or strange thrilling sensations were perceptible 

 at every step while proceeding through the ground, as long as the 

 morning continued damp. When, however, the sun became suf- 

 ficiently powerful to dry up the dew, and remove the film of water from 

 the wires, bamboos, and grass, then the wires alone conveyed the elec- 

 tricity. My experiments convince me that dry wood, earth, and 

 masonry are perfect non-conductors of this kind of excitement. Even 

 the bark of living trees seems a perfect insulator. 



Some months previous to the experiments now described, I accident- 

 ally found too (by the falling of a wire into the large tank at the Medi- 

 cal College) that when water was available, only one insulated wire 

 was requisite for completing communications. I did not omit the op- 

 portunity afforded by my experiments at the Gardens of following up 

 this curious result, and although I find the fact has also attracted the 

 attention of Professors Henry and Steinheils, these philosophers will, I 

 feel convinced, learn with interest the simultaneous pursuit of the like 

 object, in my humble investigations. 



In one experiment the electro-magnetic machine was stationed at the 

 ghat of Bishop's College, and one of its wires, but twenty-five feet 

 long, dipped in the Hooghly at the ghat. The second wire ran along 

 the dry path round through the Botanic Gardens, and terminated 

 in Dr. Wallich's library. A wire led from the river at the ghat before 

 Dr. Wallich's house, also into the library. The assistant stationed at 

 the machine was directed to make the signals in the usual manner. 

 Every signal told in the library without any notable diminution of 

 effect. 



It made no perceptible difference whether the tide was ebbing or 

 flowing ; — in several trials the damp mud even conveyed the signal un- 

 altered in force or character. 



The distance by water in the above experiment was 7,000 feet. In a 

 second set of trials the machine was placed at Sir John Royd's garden, 

 the water distance intervening being 9,700 feet, and with the same 

 results as before. {See lithographed plan No. 1.) 



In a third trial, seven miles of wire were disposed round the 

 trees of the Garden, taking in its entire boundary— starting from 

 Dr. Wallich's house and terminating in the river at Howrah ; a second 

 wire was carried from the river, at the west end of the Garden (two miles 



