172 • IMPROVEMENT IN THE 



Improvement by Though this method is undoubtedly worthy of much alters* 

 sounced." * " *' on * anc * ma ^ °^ tcn ^ e employed with advantage ; yet, when 

 a flrong charge is required, the common mode of ftemming 

 muft be frequently adopted : And as the danger in bJafiing 

 fome kinds of rocks in this manner is very confiderable, I am 

 happy to notice an eafy method of obviating one principal 

 ckute of accidental explofion, which was communicated to 

 me in converfation, a few days ago, by Mr. Thomas Fiftier, 

 a refpectable Hate merchant in this town, who allures me it 

 is infallible, 

 Caufcs of acci- The principal danger attendant on blading, does not con, 



Tfj£* e?P ^ fi Us** m liemmin g u P on t,,e char £ e of powder, but in the fubfe- 

 from the friction quent operation of drawing the iron rod, called the pricker, 

 of the iron which makes the channel lor the priming-ftraw! For although 

 ^rawing. * ne collifion of the firft fragments of Hemming fometimes pro- 



duces an explofton, yet this may be prevented by rjrevioufly 

 ramming a thick cap of paper-, &c. upon the powder; by 

 beating lightly upon the firft pieces of ftone that are thrown 

 into the hole; or by ufing thole materials for Hemming which 

 are leaft liable to give tire, fuch as rotten ftone, pieces of 

 broken pots, or burnt clay. The pricker being hard preffed 

 againft the rock, and in clofe contact wi-th the ftemming, can- 

 not be drawn out by hand, but muft be ftruck out by the 

 hammer, a ftrong piece of iron called a jumper being nrft 

 placed in an eye or loop in the higheft part of the rod, io re- 

 ceive the blows which are given in a proper direction to bring 

 it out of its place. Now it frequently happens, that the fric- 

 tion of the loweft part of the pricker againft the rock fires the 

 powder at the firft or fecond blow. When the explofion 

 happens at the commencement of ftemrning, the workman 

 generally fuftains only a partial injury; but when in this part 

 of the operation, when the powder exerts its whole force, and 



the charge may partially communicate with the fmall afcending co- 

 lumn contained in the ft raw. After this, the remainder of the ex- 

 cavation is filled, by pouring in dry fea-fand; and the explofion is 

 given, by firing the priming-ftraw in any of the various ways which 

 are in common ufe. 



" This method has been found to be equally effectual as ftem- 

 ming with any of the common materials ; and where it can be ufed 

 is certainly preferable : it is fafer, Ampler, and more expeditious." 



difperfe* 



