592 Well-Sinker's Explosion Apparatus. 



sinking wells in rocks) from the top of the well ; thus avoid- 

 ing the great danger to which they are exposed if they set fire 

 to a train at the bottom, and are then drawn up in the bucket, 

 as usual at present, by which many lives are lost. Fig. 121. 

 represents a section of a jumper hole in the rock, at the bot- 

 tom of a well : a is part of the chai'ge of gunpowder ; b is the 

 sand usually placed above the charge ; d is a tube, generally 

 a straw (filled in this case with common dry powder), which 

 is inserted into the hollow of the steel plug (e), which is 

 turned, and just fits the jumper hole, in which it is steadied 

 by a single blow of a hammer. The upper part of this plug 

 is formed to receive a common detonating cap (jf), such as is 

 used for firing fowling-pieces. There is an eye at g, to which 

 an iron wire (/?.) is fastened, and on which a cylindrical weight 

 of cast iron (of from one to five pounds' weight, according to 

 the depth or shallowness of the well) slides. The hole for 

 the wire is bored in this, at such a distance from the centre of 

 the cylinder end, as to allow it, when the wire is stretched 

 from the top of the well, to fall fairly over the cap, a little 

 inclining; to the side marked s. 



The mode of using this is pretty obvious : all being pre- 

 pared below, the well-sinker goes to the top of the shaft, slips 

 the Aveight on the wire, fastens the wire to some appropriate 

 part of the windlass, and then lets go the weight, and retires. 

 If fixed properly, it falls with its centre of gravity directly 

 over the caps ; and, exploding, it fires the blast. The steel 

 plug, weight, &c.j will not be injured by the explosion, and, 

 of course, may be used many times. 



The dotted lines at p show that the situation of the cap, 

 &c, may be changed, so as to suit either a horizontal or a 

 vertical blast, or any thing between the two. 



The whole apparatus costs but a few shillings, and, I think, 

 would be far more certain, safe, and expeditious than the 

 mode at present adopted. If objections be made to the dan- 

 ger of the plug being of steel, it may be all of copper, except 

 the part on which the cap fits, and which never touches the 

 stone. 



It is obvious that this mode of firing blasts is not confined 

 to well-sinking only, but that a little tripod stand of 4 or 5 ft. 

 in height, will form a support, from which any common 

 quarry blast may be fired from a distance with greater safety 

 and certainty, and less loss of time, than by any mode now in 

 use, so far as my knowledge goes. Horizontal or inclined 

 blasts, in a quarry, may be fired the same way as in a well. — 

 Yours, &c. — Robert Mallet. 94. Capel-Street, Dublin, 

 August 6. 1832. 



