In the November issue of The Billiard Monthly we referred to the ball contacts on the quarter inch scale only, namely: Grazing ball, for which aim is taken one inch outside the edge of the object ball; quarter ball, for which aim is taken half-an-inch outside the edge of the object ball; half-ball, for which aim is taken at the edge of the object ball; and three-quarter ball, for which aim is taken half-an-inch inside the edge of the object ball. There are, of course, intermediate contacts, and these are reckoned by eighths. These are, however, comparatively seldom used, and chiefly at short range.
To make a seven-eighths (or almost full) contact, aim must be taken three-quarters of an inch inside the edge of the object ball or a quarter of an inch from its centre; to make a five-eighths contact aim must be taken a quarter of an inch inside the edge of the object ball; to make a three-eighths contact aim must be taken a quarter of an inch outside the edge of the object ball; and to make an eighth contact aim must be taken three-quarters of an inch outside the edge of the object ball.
Perhaps at this point the exact meaning of half-ball and other terms denoting degree of contact may be referred to.
A half-ball stroke means one in which, at the moment of contact, half of the cue ball covers or eclipses half of the object ball. In like manner the fuller than half-ball contacts, namely, the three-quarter and the full ball contacts, together with the intermediate five-eighths and seven-eighths contacts, mean contacts in which the object ball is covered by the cue ball to the extent indicated by the term; and the same thing applies to the quarter and grazing ball contacts, together with the intermediate three-eighths and one-eighth contacts.
This may seem elementary, but it is quite essential, and is often insufficiently understood or ignored. There is no stroke in billiards that cannot be made by means of one or other of the nine contacts that have been described and seventy-five per cent. are to be made by the use of the half, three-quarter, and quarter ball contacts only. The great thing to remember is that, with all plain strokes, the point of contact is midway between the point of aim and the centre of the ball, and that it is along a line from this point that the object ball takes its course.
The three great essentials in the making of a plain stroke break are:—(1) Knowledge of the nine aims and contacts, and the effect of each upon both cue and object ball; (2) accurate and light delivery of the cue; and (3) the strength requisite to leave the object or cue ball, or both, in a desired position. This desired position, as regards the object ball, may be (1) somewhere near the central line of the table, or (2) near a pocket, or (3) near a second object ball which needs to be extricated from a non-scoring position.
As regards the cue ball, especially after a pot stroke, a desirable thing is to leave it somewhere "on the line," as it is called, and which means an imaginary line drawn from the upper shoulder of a middle or top pocket to the billiard spot—typical and easy half-ball in-offs. The "strength" required to leave a ball in good scoring position varies according to the distance to be covered and the amount of contact between the balls. The object ball may be scarcely moved, or it may be driven in and out of baulk.