18 THE ELECTRIC TELEGRAPH. 



experiments may be repeated ad infinitum even after the pile 

 has been mounted some hours, provided the cloth retains 

 some moisture. 



3rd. It produces chemical effects with an energy propor- 

 tional to the number of elements accumulated. 



The zinc disc which forms one of the extremities of the 

 pile, being that which, in communication with the condenser, 

 gives a positive charge, has been called the positive pole, and 

 the copper plate at the bottom of the pile the negative pole. 



23. Immediately after the receipt of Yolta's letter, by the 

 President of the Royal Society, a pile was constructed on this 

 principle by Mr. Nicholson (the conductor of Nicholson's 

 Journal) and Sir Anthony Carlisle. A drop of water being, 

 on one occasion, used by them to make a good contact 

 between the conducting wire and a plate of metal with which 

 they were experimenting, Carlisle observed a disengagement 

 of gas from it. Further experiments discovered very shortly 

 the decomposition of water by the electric current. Thus 

 was chance once more on the stage in promoting electrical 

 discovery, and this time the magnificent investigations of 

 Humphrey Davy were the result. 



24. In the year 1808, Herr S. T. Sommering communi- 

 cated to the Academy of Sciences in Munich his invention 

 of a system of telegraphing based upon the discovery of the 

 British chemists, Nicholson and Carlisle,* that water is de- 

 composed into its constituents of oxygen and hydrogen by 

 the voltaic current. 



At the station which was to receive signals were arranged, 

 in a narrow vessel of water, thirty-five glass tubes, each con- 

 taining a gold point, twenty-five marked with letters of the 

 alphabet, nine with numerals, and one with a zero. From 

 each point an insulated wire was led to a metal terminal at 

 the transmitting station. 



To send a signal it was only necessary to bring the two 

 poles of a voltaic pile to two of the terminals in question. 

 The current passing from one terminal traversed its line 

 wire to the voltameter at the receiving station, where it 



* "Galvanism," by Sir W. S. Harris, p. 35. 



