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fluid, this part of the wire is made very thin, or what is better, 

 a short piece of fine steel wire is attached to the copper 

 conductor ; steel wire is to be preferred, because it is easily 

 heated, and scintillates by the passage of the electric fluid 

 through it. 



But as fixing such a piece of wire upon the main conductor 

 for every operation would be troublesome, a cartridge is used, 

 which can be attached to it in less than a minute ; this 

 cartridge consists of a tin tube, about two inches long and 

 half an inch in diameter, in which is fitted two wires con- 

 nected together in the tube by a fine steel wire, a quarter or 

 half an inch longer ; the tube is then filled with gunpowder 

 and closed by a cork at both ends; which may be further 

 secured by varnish, should it it be requisite to fire the charge 

 under water ; the ends of the wires projecting from the tube 

 are to be attached to the long copper wire before described, 

 as the main conductor. The cartridges are made in this form 

 for the saving of time in blasting, as the men can prepare a 

 number of them prior to the commencing of their operations 

 on the rock, and being well corked and varnished, they may 

 be kept any length of time without sustaining injury. 



I have alluded to my new process of tamping ; one part is 

 based upon the curious fact, that if a tube of small diameter 

 and moderate length be filled with dry sand, it will require 

 an immense force to drive out the sand with a rammer . 

 , indeed so great is the resistance, that if the tube be two feet 

 long and about one inch diameter, no force that can be applied 

 will drive the sand out, the tube will more readily burst than 

 the sand give way ; this peculiar property in sand can be 

 applied with great benefit to actual practise ; for in tamping, 

 the dangerous and tedious process of ramming down stones 

 and gravel may be abandoned, and the safe and ready one 

 substituted, of merely pouring dry sand into the hole, which 

 requires no ramming ; the operation is performed in half a 



