BLASTING OP ROCKS, - ^3^ . 



communication with the fuze, and then to ram up the re- 

 mainder of the hole with ftone pulverized by the operation of 

 ramraing it; after which the wire is withdrawn and the prim- 

 ing introduced. 



This is a tedious operation, often attended with danger, and >s tedious, dan- 

 frequently the labour and powder is loft by the priming hole fgr^in.^ ""' 

 being obflruded in ftriking out the wire with a hammer. 



I had been informed that inftead of this tedious operation} Loofc fand pro- 

 the blafting had been effeaed by introducing a ftraw filled with P^^*^^ .'"*"<! °^ 

 fine powder, and then filling the hole with loofe fand, 



I hardly could believe this, conceiving that the part where 

 there would be the leaft refillence would firfl yield to the ex- 

 plofion, and therefore that the loofe fand mufl of courfe be 

 blown out. 



But in the month of Augufl laft I tried the experiment in Succefs of the 

 fome very hard rock at Fortwilliam and it completely fuc- experiment, 

 ceeded: I fince then have tried it on the lime rocks at Briflol 

 with the fame effe^. 



A kw days (ince, wifliing to know how fmall a quantity of Oak 20 inches 

 fand would produce the efFea, I caufed a hole of l| inch in f^^^^J^ f^^^^ 

 diameter and 12 inches deep, to be bored in a knotty piece of charge of 3 

 oak of about 20 inches in diameter and charged it with three *"^^*^ ^*"*** 

 inches of powder, and upon that four inches of fand, intend- 

 ing (as I fuppofed that mufl be blown out) to repeat the quan- 

 tity of fand inch by inch to the quantity that would be, fuffi- 

 cient, but to my great furprize, it fplit the piece with great 

 violence into fix pieces, 



I then repeated it on a fimilar log of oak, with a charge of The fame 

 two inches of powder, and three inches of fand; it fplit the *=^^^^^^^'^ ^'^^^ 

 piece in two, and fent half of it into the air to the diftance of 

 forty yards. 



I think it may puzzle a philofopher to account for this: I Conjeaure as to 

 bave fuppofed that the fand in contadl with the powder, firft 

 moving, the particles wedge each other fall: before the motion 

 has time to be communicated to the whole. 



I have reafon for thinking that a much lelTer quantity of Lefs powder 

 powder will produce the efFed in this way than by the common ^'^^ f^ohMy 

 method; for as it lies loofe in its chamber and makes itfelf this way. 

 more room by a little yielding of the fand, the whole will take 

 fire, and efpecially if when half the charge is put in, the ftraw 

 be introduced and then the other half charge, fo that it may 

 take fire in the middle of the charge. 



That 



