Fig. 3 is a round hole drilled either by hand or otherwise, preferably otherwise, because an important point is to get it round.  Fig. 4 is the improved form of hole, and this is made by inserting a reamer, Figs. 5 and 6, into the hole in the line of the proposed fracture, thus cutting two V-shaped grooves into the walls of the hole.  The blacksmith tools for dressing the reamers are shown in Fig. 7.  The usual method of charging and tamping a hole in using the new system is shown in Fig. 8.  The charge of powder is shown at C, the air space at B and the tamping at A. Fig. 9 is a special hole for use in thin beds of rock.  The charge of powder is shown at C, the rod to sustain tamping at D, air space at BB, and tamping at A.

[Illustration:  Fig. 7]

Let us assume that we have a bluestone quarry, in which we may illustrate the simplest application of the new system.  The sheet of stone which we wish to shear from place has a bed running horizontally at a depth of say 10 ft.  One face is in front and a natural seam divides the bed at each end at the walls of the quarry.  We now have a block of stone, say 50 ft. long, with all its faces free except one—­that opposite and corresponding with the bench.  One or more of the specially formed holes are put in at such depth and distance from each other and from the bench as may be regulated by the thickness, strength and character of the rock.  No man is so good a judge of this as the quarry foreman who has used and studied the effect of this system in his quarry.  Great care should be taken to drill the holes round and in a straight line.  In sandstone of medium hardness these holes may be situated 10, 12 or 15 ft. apart.  If the bed is a tight one the hole should be run entirely through the sheet and to the bed; but with an open free bed holes of less depth will suffice.

[Illustration:  Fig. 8, 9]

The reamer should now be used and driven by hand.  Several devices have been applied to rock drills for reaming the hole by machinery while drilling; that is, efforts have been made to combine the drill and the reamer.  Such efforts have met with only partial success.  The perfect alignment of the reamer is so important that where power is used this point is apt to be neglected.  It is also a well known fact that the process of reaming by hand is not a difficult or a slow one.  The drilling of the hole requires the greatest amount of work.  After this has been done it is a simple matter to cut the V-shaped grooves.  The reamer should be applied at the center, that is, the grooves should be cut on the axis or full diameter of the hole.  The gauge of the reamer should be at least 11/2 diameters.  Great care should be taken that the reamer does not twist, as the break may be thereby deflected; and the reaming must be done also to the full depth of the hole.