1840.] The Galvanic Battery. 1157 



ductility, flexibility, and cheapness. Tiie dimensions and other details 

 connected with the conductors are determined by the nature of the 

 circumstances under which they are to be employed, which may be 

 classed under three heads : — 



I. When the conductors are simply led along the surface of the 

 ground, as in blasting rocks in quarries. 



II. When the conductors are led under the surface of the ground, 

 as in military mining. 



III. When the conductors are immersed in water, as in sub-aqueous 

 mining operations, for the removal of sunken vessels, or rocks in the 

 beds of navigable rivers, &c. 



In the first case, the conductors require no protection whatever, and 

 may be formed of naked wires, care being however taken that while 

 the operations are in progress, no metallic contact takes place between 

 them. This might be effectually guarded against by inserting corks or 

 pieces of wood between the two wires, at convenient intervals, through- 

 out their length. 



Our information relative to the best arrangements for conductors 

 employed in military mining operations is still very limited, a few 

 experiments due to Colonel Pasley being all that has yet been 

 published on this branch of the subject. It is only at establishments 

 where military works are continually being executed, that facilities for 

 experiments of this kind can be obtained, and it might be worth while 

 on the part of Government to sanction a series of them, at the head- 

 quarters of the Sappers and Miners at Delhi, where, during the practice 

 season, all the requisite facilities would be readily available. Colonel 

 Pasley employed the same conductors in his military mining expe- 

 riments as in his sub-aqueous explosions; they were elaborately in- 

 sulated by repeated applications of water-proof composition, tape, and 

 spun yarn, as will be more fully described hereafter. Although I feel 

 considerable hesitation in venturing to express an opinion on a strictly 

 experimental point, I am yet inclined to believe that, especially in dry 

 earth, the minimum of insulation will suffice ; a single covering of 

 itarred tape to each wire, would, I believe, prove effectual under such 



! circumstances. 



I In the third and last case, when conductors are immersed in water, 



j the arrangements for insuring their efficiency are necessarily more 



7 I 



