1162 The Galvanic Battery. [No. 108. 



Experiment 2. The same conductors reduced to 50 feet. 

 2 cells produced immediately ignition of the cloth. 



1 cell singed the cloth, and made it black, but could not 



ignite it. 



2 cells caused the powder to explode directly. 



I cell caused the powder to smoke, but could not ignite it. 

 Experiment 3. Conductors of single wires, l-20th of an inch in 

 diameter and 50 feet in length each, were now employed, and the 

 following results obtained : — 



4 cells ignited saltpetre cloth immediately. 



3 cells merely singed it. 



4 cells ignited powder immediately. 

 3 cells had no effect whatever. 



Experiment 4. The same conductors were employed, but thin brass 

 wire was substituted for platinum. 



5 cells caused the ignition of saltpetre cloth. 



6 cells ditto of powder. 



This experiment involves a question of some importance ; viz. the 

 substitution of some other material for platinum, which in this country 

 is most exorbitantly expensive. An interesting series of experiments 

 might be made on this point, by which our resources could not fail 

 to be increased. 



With the full power of a 12 cell Battery, I have frequently ignited 

 charges of powder in water, at distances varying from 450 to 500 feet, 

 employing insulated conductors ; and by such a Battery was the final 

 destruction of the "Equitable" effected, where the conductors were 150 

 feet in length, 120 of which were placed horizontally, the remaining 30 

 vertically in the water. 



Before concluding this Section, it may be well to describe some 

 expedients which, under certain circumstances, have been employed 

 for the purpose of diminishing the lengths of conductors. The idea of 

 effecting the completion of the galvanic circuit by means of a self-acting 

 mechanical arrangement, appears to have originated with Mr. Martyn 

 Roberts, who claims to have been one of the first who applied the 

 Battery to useful purposes. With the details of Mr. Roberts' apparatus 

 employed in his blasting experiments in Craig Leith Quarry, I am not 

 sufficiently conversant to be able to describe it, but in blasting, such 



