Lesley.] lOU [March 7, 



times the space it did in the solid, it follows that the refuse heap will 

 increase beyond the limits of the area quarried ; this, however, is- pro- 

 vided for in the rise of the hill as the work advances. Retaining walls 

 will also be needed, from which to dump the ore into the railroad cars ; 

 these will be made of posts and planks backed up with the refuse. 



The lay of the measures as a whole and their individual structure are 

 each of a character favorable to such a mode of procedure. The jointed 

 condition of the sandstone, when not in thin plates, will allow the free 

 use of the crow-bar to advantage, but the shales operated on from above, 

 that is, perpendicular to their bedding, will be tough to the pick-axe ; 

 holed under, or worked at on the face will give the best result. 



While it may not be absolutely necessary to resort to blasting, a 

 judicious use of gunpowder will be of great advantage. A series of holes 

 put down to the bottom of the ore, or to the bottom of the lower interval, 

 at a foot from face of stripping, and loaded so as to loosen the mass 

 only, would make easier work for the crow-bar and pick-axe, and would 

 not make the ore any the less easy of separation from the refuse. Each 

 quarryman has generally his own notion of the quantity of powder to be 

 used in a given case, seldom deduced from any fixed data. Practice has 

 shown that the quantity must be increased as the cube of the mass to 

 be blasted ; from which it is laid down that the cube of the line of least 

 resistance in feet, divided by two, equals the necessary quantity in 

 ounces ; less, however, will answer the purpose here ; well directed ex- 

 periment at the beginning will guide the application of the rule. 



In estimating the cost of quarrying these ore beds, we have tolerably 

 well-defined data in the ores and intervening strata, but a fluctuating 

 element in the amount of covering. Taking, however, as an example 

 the section before given, I am of opinion that at the present rate of 

 wages, the ore may be put into cars on the quarry for — in other words, 

 that the cost of production will be — one dollar twenty-live cents per ten 

 ($1.25). With a less thickness of ore or increased covering the cost of 

 production will be increased ; 36 inches of ore, the average estimated, 

 with the same amount of covering, will cost one dollar fifty-four cents 

 ($1.54). 



In the more highly inclined and heavier covered beds, we have con- 

 ditions which render mining necessary, and the method I would adopt 

 would be that which, in coal and the clay ironstone bands, is called 

 Long wall ; for whether mined in shorter or longer "banks," called by 

 some "stoops," the same principle prevails, namely, that of mining out 

 the whole of the mineral, packing the refuse gob or goaf, in the space 

 mined, and putting out the ore either by shoots or cars, agreeable to the 

 angle of inclination at which the measures lie. 



With such inclinations as wherein cars cannot be made use of in the 

 gob roads, a drift (tunnel) will be put in above water-level, and along 

 the strike of the ore, of sufficient capacity for the running of cars, say 7 

 feet wide at the floor, battering inward to 5 feet at the roof, and 6 feet 



