342 History of Mechanical Inventions and 



ing at the quarry, and lowering it down by means of a string, I found that 

 it would not descend more than seven feet ; and, to add to my mortification, 

 I found that the lower bore was not more than nine inches in depth, in- 

 stead of eighteen, as I had directed. 



However, with all these disadvantages, I was desirous to have the ex- 

 periment tried, more especially as the first objection accorded with my own 

 ideas respecting the proper position of the cone, that it should be at least 

 two feet from the bottom of the large bore ; this, however, I intended for a 

 second experiment, so as to compare the difference, if any, but necessity 

 made it the first. 



Accordingly, matters being all prepared, the cone was let down into the 

 bore, and forced down to twenty inches from the bottom, a small piece of 

 flannel was put down upon it, in order to prevent any of the gunpowder 

 from passing into the lower chamber, that is, below the cone. The 

 charge which the workman informed me was used for such a depth of 

 bore, was nine pounds weight of gunpowder, but I requested him to use 

 only six, which quantity was had recourse to, and every thing else con- 

 ducted in the ordinary way. 



At last the usual signal of the blowing of a horn was given to all in 

 the great cavity of the quarry below, as well as all in the surrounding quar- 

 ries, to keep at a distance. Fire was then communicated to the match, 

 and in about a minute the whole went off with less noise than I could 

 have conceived, considering the quantity of gunpowder ; but the proprie- 

 tor of the quarry made a remark, before I had time to speak on the sub- 

 ject, " that he was sure that this was a good blast from the hollow sound." 

 Being at a considerable distance from the rock, we could not discover what 

 had actually taken place, but from the altered appearance we could foresee 

 great demolition of it. 



On our arrival, by very rugged and uneven paths, we found most extraor- 

 dinary devastation indeed ! a mass of rock exceeding, according to the work- 

 men'smeasurement, one hundred tons, was thrown offto the distance of three 

 feet from the solid rock, and a quantity of fragments, none less than a ton, 

 and many of them equal to twenty, were thrown to a considerable distance 

 beyond this great mass, and one piece, from the upper surface of the rock, 

 was thrown into the air directly upwards, in the most beautiful circular di- 

 rection, to the distance of one hundred feet, as was judged by those who 

 witnessed it. All these detached blocks were measured by the workmen 

 in the rou"h way that they are accustomed to do, and they were calculated 

 to be about another hundred tons. But the most remarkable circumstance 

 (to the quarriers) was the immense split or rent given to the whole 

 rock in every direction, for it was traced to twelve feet beyond the bore, 

 an occurrence which they had not witnessed before. From this unexpect- 

 ed occurrence they had no great trouble in separating a large quantity of 

 this rock by the simple use of the mechanical power of the lever and wedge, 

 by means of which some very fine blocks of stone were separated to the 

 extent of another hundred tons. Thus showing, in the most incontestible 

 manner, that this plan is more efficient than any that has been proposed 



