100 On Blasting Roch, and Tamping, 



The use of copper nails vvouki prevent this ; but though 

 often tried, tlie miners, from their being not quite so con- 

 venient, will not continue the use ofthem. 



The plan of adding to the resistance of tamping by load- 

 ing the aperture of the hole, as proposed by M. Gillet 

 Laumont, is in continual use among the Cornish miners, 

 but in a more simple and cflfectual way than he suggests ; 

 and it is certain that some rock could not be blasted without 

 this assistance. 



M. Pictet, it is said in the same article of the Philo- 

 sophical Journal for July, has conceived that a more 

 effective explosion for the purposes of mining might be 

 obtained by leaving a partial vacuity, or by the chamber 

 not being completely filled by the gunpowder. Now this 

 idea is directly in opposition to the received opinion of per- 

 sons conversant with these operations; but not having made 

 any accurate experiments on the subject, I shall only state a 

 case that appears to be in point. We are frequently obliged 

 in very wet ground to use gunpowder in cartridges of thin 

 tinned plate ; and as these cannot be made to fill up the 

 diameter of the chamber completely, we obtain, what he 

 conceives is desirable, a less concentrated exj)losion; but so 

 far is it from being beneficial, rliat every miner will use 

 every other means before he employs gunpo*Vder in this way, 

 because it is universally found to require a much greater 

 quantity for a given effect, and much more, I conceive, than 

 can be attributed to the small degree of resistance offered by 

 the material of which the cariridge is 'oruK d. 



The most promising scheme for facilitating the operation 

 of blasting rock that I have heard of, has been suggested 

 very lately to me by a friend whose mechanical skill and 

 injrenuitv are well known, and who has lately applied with 

 surprising dexterity that powerful agent gunpowder at great 

 depths under water. 



A sort of powder is made of double or treble the 

 strength of common cannon powder, and if this be applied 

 to the uses of mining, he thinks that holes of half the usual 

 capacity might contain sufficient charges in equal lengths. 

 If so, it is certain that such holes, being considerably less in 



diametcir 



