BUILDING AND ORNAMENTAL STONES. 



325 



The illustration shows the drill-rotlor s[)in(rie placed near the base of 

 the machine, and so as to bore horizontally. At one end of the spindle 

 is the drill-head, armed with carbons, and snpi)lied with small aper- 

 tures or outlets for water. At the other end of the spindle is attached 

 a hose for supplying water to the drill-head. A rapid revolving move- 

 ment is communicated to the drill-spiudlo by the gears shown. The 

 s])eed and feed movement may be regulated by the o^ierator with reici-- 

 ence to the hardness or softness, coarseness or fineness, of the matciial 

 to be boi'od ; ;iiid the iVed movement may be instantly reversed ati)l«';is- 

 nie. The machine is so constructed that the drill-spindle niay be re- 



Diamouil (ladder. 



moved .and another inseited in the same holder, adjusted to bore in the 

 opposite direction, the boiing api)aratus being driven by a double-cylin- 

 der engine. A continuation of one of the piston-rods through the cylin- 

 der forms the plunger to a small pump placed above the cylinder, which 

 supplies water to the boiler and forces water through the drill spindh^ 

 and head. These jets of water wash out all the borings made, and keep 

 the drill-head from heating. The usual feed of this drill in marble is 

 from 4 to 5 inches per minute. 



k^till another style of gadding-machine isused in the Vermont quarries, 

 and which is but an especial adaj)taition of the eclii)se drill shown on 

 page 32G. It is claimed that this machine will "put in holes close to the 



