Democratic Sentinel, Volume 19, Number 26, Rensselaer, Jasper County, 5 July 1895 — WITH FINE CHISELS. [ARTICLE]

WITH FINE CHISELS.

Thirty Pounds of Stone Broken Up by One Pound of Wood. At Bangalore, in Southern India, the quarrying of granite slabs by means of wood fire has been brought to such perfection that an account of the method is interesting. The rock forms solid masses uninterrupted by cracks for several hundreds of feet, and when quarried over an area is treated as follows: A narrow line of wood fire, perhaps seven feet long, is gradually elongated, and at the same time moved forward over the tolerably even surface of solid rock. The line of the general splitting of the rock is indicated by piles of light wood, which have been left burning in their position until strokes with a hammer indicate that the rock in front of the fire has become detached from the main mass underneath. The burning wood is then pushed forward a few inches, and left until the hammer again indicates that the slit has extended. Thus the fire is moved on, and at the same time the length of the line of fire is increased and made to be convex on the side of the fresh rock, the maximum length of the arc amounting to about twenty-five feet. It is only on this advancing line of (ire that any heating takes place, the portion which has been traversed being left to itself. This latter portion is covered with the ashes left by the wood, and with thin splinters which have been burst off. These splinters are only about one-eighth of an inch in thickness and a few inches across. They are quite independent of the general splitting.of the rock, which is all the time going on at a depth of about five inches from the surface. The burning lasts eight hoars, and the line of fire advances at the average rate of nearly six feet an hour. The area actually passed over by the line of fire is four hundred and sixty square feet, but as the crack extends about three feet on either sid# beyond the fire the area of the entire slab which is set free measures about seven hundred and forty square feet. All this is done with, may be. about fifteen hundred weight of wood. Taking the average thickness of the stone at five inches, and its specific gravity at 2.62, the result is thirty pounds of stone quarried with one pound of wood.