In Greek times the iron chisels are shorter and merge into wedges (39).
Where the rail-gauge is narrow and great weight is not desired, blocking girders are provided across the under side of the truck; these are arranged so that, by means of wedges or screws, they can be made to increase the base.
In driving levels it is necessary to cut grooves vertically parallel to the walls, a process known as shearing; but the most important operation is that known as holing or kirving, which consists in cutting a notch or groove in the floor of the seam to a depth of about 3 ft., measured back from the face, so as to leave the overhanging part unsupported, which then either falls of its own accord within a few hours, or is brought down either by driving wedges along the top, or by blasting.
Most of it was made, by bursting the rock by means of wooden wedges, through the solid granite, and its outside parapet was supported by walls of brick resting on ledges far below.
In shallower masses a groove was run, and then holes, apparently for wedges, were sunk deeper in the course of it; whether wetted wood was used for the expansive force is not known, but it is probable, as no signs are visible of crushing the granite by hard wedges.