ART OF BLASTING ROCKS. 171 



.From the refults of all the experiments, of which I have Conclufion. 

 juft given an account to the clafs, we may conclude, that the j^ ^^ l a J s ° 

 quantity of heat excited or communicated by the folar rays is as the light ab- 

 always, and under all circumftances, as the quantity of light 

 that difappears. 



III. 



Obfervations on blafting Recks ; tcith an Account of an Improve- 

 ment, whereby the Danger of accidental Explofion is in a great 

 Meafure obviated. By Mr. William Close. From the 

 Author. 



To Mr. NICHOLSON. 



SIR, Dalton, Oa. 14-, 1805. 



JL HE method of confining the force of gunpowder by a co- Practice of blaft- 

 lumn of fand in blafting rocks, has been feveral years ufed in £8^ fandin 

 this part of Furnefs : At one time it was a very favourite prac- 

 tice; but at prefent, from the prejudices or indifference of 

 workmen, or on account of the little danger attendant on 

 working lime-flone in the common manner, it is lefs in 

 repute. 



About two years ago, fuppofing this method not to be ge- noticed by the 

 nerally known, I drew up a fhort account of it, and fliould au ^ hor elie - 

 have lent it to the Philofophical Journal, had it not been con- 

 nected with other mifcellaneous matter, which I had given to 

 Mr. G. Athburner, the printer and proprietor of a new edi- 

 tion of Weft's Antiquities of Furnefs, in which work the pro- 

 cefs is defcribed and recommended*. 



Though 



* The pafTage alluded to is as follows, p. 393. " In breaking 

 up the loofe rocks upon Baycliff Haggs, after the enclofure of that 

 common, a method of employing fea-Iand, for the purpofe of con- 

 fining the force of gunpowder in blafting, was ufed, which does 

 not appear to be generally known, though it was undoubtedly in 

 ufe in other parts before it was adopted in Furnefs. The method 

 is briefly this : After the excavation is made in the ufual manner 

 with a borer, the charge of powder is poured in j and a priming- 

 ftraw of a proper length, filled with powder, is placed in the hole., 

 having one of its fides near the lower end fo cut or thinned, that 



the 



