Processes in the Useful Arts. 341 



better understood by an inspection of Fig. 2. When this part of the pro- 

 cess is completed, the next operation is to apply the wedge ; which is ac- 

 complished by a cone of steel, at first dead hardened, but afterwards brought 

 back to spring temper. This cone, Fig. 3. it is unnecessary to say, must be 

 in proportion to the size of the bore at its base in diameter, and its apex 

 of a size so as to enter at least one inch into the lower chamber or 

 bore. When the charge is to be made, the cone is to be lowered down, 

 till it meet with the resistance at the bottom of the bore, as represented in 

 Fig. 4. Then the gunpowder is to be put in, and the whole completed 

 in the usual way, or according to the plan that I have stated, but as that 

 has not been put in practice, I can only state the result of the common 

 mode of charge with the cone. 



Having been informed by the quarrier that a two inch and an half bore 

 would be the most proper size to try the effect of it, I gave orders to have 

 the cone made exactly of these dimensions at its base. But, on attempt- 

 ing to pass it down, by means of a piece of cord, into the aperture, I found, 

 to my surprise, that it did not proceed quite one-third of the depth of the 

 bore; consequently, to my great disappointment, it could not be used at 

 this time ; but as all things were prepared for the destruction of the rock, 

 I remained till the blast was made, by which there was a great alteration 

 in the appearance of the rock ; for, instead of being one solid body, it was 

 now a heap of confusion, of fragments more or less in magnitude, all of 

 which seemed to have been thrown off not lower than two-thirds of the 

 depth of the bore. 



This last circumstance gave me great encouragement to procure another 

 opportunity of trying the effect of the wedge or cone. 



After a lapse of several months, the quarrier called upon me, and said 

 that he had now another opportunity of trying the new method, as he called 

 it ; accordingly, I gave him instructions to make his bore to the depth that 

 he thought right, and then to measure the diameter of it at the bottom, 

 for I had not learned till now that no man could make a cylindrical bore 

 to any extent in stone. That as it went down it became narrower, in other 

 words, it became quite oval, and therefore unfit for my purpose. Now, on 

 reflecting on this circumstance, it occurred to me that means might be 

 devised to obviate this circumstance, either by employing a. jumper (as the 

 workmen call these tools) of a different construction originally, or, after 

 the bore is made with the common tools, to use the one that I would re- 

 commend ; and an inspection of Fig. 5, 6, will show what I mean. By per- 

 severing in the same manner that the first tool was used, the bore will at 

 last be made quite cylindrical. But as this does not seem to be of any great 

 consequence in regard to the general result, seeing that the inconvenience 

 of an oval bore can be easily obviated by the smallest attention on the part 

 of the operator, I have not given myself any trouble on this score. 



Next day the workman called and mentioned that the depth of the bore 

 was nine feet, and its diameter at the bottom was two inches, while at top 

 it measured half an inch more and rather better. Accordingly I got the 

 cone made very exactly to his measurement at the bottom, I tit. on arriv- 



