yS On Blasting Rocksy and Tamping, 



lity of gunjjovvder being certainly greater in those holes the 

 mouths of which are lower than the end which contains the 

 charge. This fact has frequently been shown by a charge 

 in a detached piece of rock confintd by tamping, as the 

 miners call it, in the usual way, and fired with the mouth 

 of the liolti upwards. A certain quantity of tamping will 

 in this position be blown out, and the rock remain entire. 

 tf ihe same hole be recharged with the same quantity of 

 powder, and tamped so as to present an equal resistance, 

 the rock will be torn to pieces by merely altering its posi- 

 timi, so that the charge may lie higher than the mouth of 

 the hole. Thus it may be inferred, that in firing artillery 

 there is more danger of bursting guns when they are laid with 

 their muzzles depressed, than when pointed at any degree 

 of elevation. 



Holes for blasting in mines are so frequently very wet as 

 to preclude the use of sand where other circuni stances 

 would favour it; for though, by violently compressing tough 

 clay into the fissures, the portion of the hole that is to con- 

 tain the gunpovvder may be made dry, yet to render it so 

 throughout its whole length would be aprocess considerably 

 too tedious. Here the advantage of applying clay for tamp- 

 ing is very great. The hole is instantly filled up with a 

 water-tight substance, and an opening for the fuse is made 

 through it with an iron rod, by a pressure so gentle as to 

 hazard no explosion in the performance. 



Clay is likewise more likely to be used by miners than 

 sand, if they are acquainted generally with its effect, from 

 its being always at hand, it being so necessary to the other 

 operations of boring and charging holes that it is always in 

 use where blasting is 2:oing on ; and the difficulty of intro- 

 ducing any substance that requires the least exertion to pro- 

 cure or manage among workmen is well known, whatever 

 safctv crease it may afford them. 



The French engineers pretty accuTately describe the cases 

 in whi<?h'sand will fail in its effect; that is^ eitiier wbenj,!tb;e 

 hole is bored to a small depth, so that the quantity of gun- 

 powder required to break the rock occupies such a length 

 of 4t ^ not to afford s^-acg for a sulBcient coluiBWoif sand^ 

 ^> .■•.•^.i)i<i .an ,< or 



