Example B, though not of so common occurrence as A, is also an excellent practice stroke.
Ball 1, 5½ in. from cushion 3, 21½ in. from the bottom cushion.
Ball 2, 4 in. from cushion 3, 33 in. from the bottom cushion.
Ball 3, in front of the left top pocket, 3 or 4 in. from it. Play a centre ball stroke, about half-ball on 2, with strength to carry 1 to 3—say a free No. 1. Ball 2 will double from cushion 3 and join 1 and 3 near the left top pocket.
In this stroke accidents may happen, and if it be missed by a hair’s breadth the adversary will rejoice. Ball 3 may be cannoned into the pocket and ball 2 may also go in; but, if played often, the result will generally be satisfactory and the stroke is therefore a fairly sound one. If ball 3 were the red, it would be prudent to play so as to leave ball 2 somewhat behind and thus reduce the danger of losing it in the pocket. A little consideration will show that the varieties of this stroke are numerous, and that by means of some of them the three balls may be brought to the top of the table.
The strokes shown in Diagram XV. exemplify that most useful class of cannons in which the velocity of ball 1, struck often with considerable force, is almost wholly transmitted to ball 2, and 1 retains little more than is required to reach 3. This is achieved in the first place by playing as full as the cannon will admit of on 2, and next by a peculiar use of the cue, which the French term arrêté because it is grasped and not permitted to follow the ball more than an inch or two after delivery. The stroke is a stab, and its intensity can be varied by raising the butt of the cue. The point of ball 1 to be struck is, as before, the centre, but delivery instead of being horizontal is at a smaller or greater angle with the surface of the table. The stroke is made as though the striker desired to stab the ball through its centre to the table. It springs away with more life than can be communicated by a horizontal stroke, and parts with that life on impact with 2 more readily, and therefore expires or comes to rest on reaching 3 with greater certainty. The stab is not required in every case, but where ball 2 has a long path to travel and ball 3 is at a right angle from 2 or less, it cannot be dispensed with. Classified as a stroke, it may be placed between the horizontal centre and the screw, which will be described in the next chapter, whereby ball 1 is made to return towards the point of the cue after impact with 2.
Diagram XIV.
A simple form of these cannons is shown at A on this diagram. No measurements are required, as the position is perfectly simple and equally good for practice when varied according to pleasure. It can be conveniently played when ball 3 is on the pyramid spot, ball 2 about 6 in. from it and rather nearer the player, ball 1 being between the player and 2 near the latter as shown. Play ball 1 nearly full on 2 with strength sufficient to cause its return from the cushion to 3, which 1 should reach but scarcely move. When played as shown across the table the stroke is always a gentle one, and when the balls are close to the cushion from which 2 has to return it must be played very softly indeed. The usual faults made in playing are that 2 is struck too hard and too fine, the result being that the three balls separate instead of coming together.
For B, a pretty little stroke useful in turning the corner at the left top pocket, the following measurements will help in placing the balls, which can however be set up from the diagram with sufficient accuracy.