Another method to adopt when playing the half-ball stroke up and down the exact centre of the table when the object ball is 23 inches from baulk on the central line and the cue ball is at one end of the baulk semi-circle is now to be described.
If the player aligned the cue on the central line of the table instead of towards the middle pocket, the object ball, if struck fairly in the middle with the cue would naturally travel along the desired central route, and many amateur players, before potting, walk round to this straight pot position and take their bearings therefrom. A professional never does this, and it really tells no one more than he can ascertain without any such preliminary pilgrimage.
All that he has to do as he settles down to the stroke is to imagine for a moment that the cue is aligned, not as he is actually holding it, but as it would be aligned if he were punching the object ball with it for a straight pot.
Standing for the middle pocket position already described he sees at a glance that this punch would hit the ball (as viewed from where he is standing) exactly half-way between its centre and its outer edge, and he knows at once that, as all aims must be twice as far from the centre of the ball as is the required point of contact, the outer edge is the point to aim at.
The same rule applies to all other aims and can be proved from the same central table position of the object ball. For a dead full aim and contact the cue ball would, of course, be on the middle baulk spot; for a three-quarter ball aim it would be mid-way between the end and the middle spot; for a quarter-ball aim it would be the same distance outside the corner spot; and for a grazing ball it would be the same distance outside the baulk corner spot as the centre baulk spot is inside of it.
Either of these aims if properly made and complete must indubitably drive the object ball up and down the exact centre of the table. All intermediate aims are proportionate and each shifting, by a shade under 1½ inches, of the cue ball along this 23 inches of the baulk-line means the variation of precisely one-eighth of an inch in the point on or off the object ball that is aimed at.
It is well worth while for the student who really desires to get all possible potting angles, aims, and contacts into the eye, to take a strip of paper 11½ inches long, double it three times, and lightly mark the baulk line at the folds both inside and outside of the baulk semi-circle with a piece of tailor's chalk. The two midway marks (representing the three-quarter ball and the quarter-ball aims) should be the longest and those next but one to them the next longest, as these are quarter-inch aims and more easy to locate and more frequently required than the eighth-inch aims.
The extreme importance of this preliminary practice will be fully realized when the attack on the middle pocket commences and the effort is made to guide the red ball at the same time up and down the neighbourhood of the central line of the table. Until the ball divisions, aims, and contacts have been carefully studied, and the accuracy or otherwise of the cueing and of the strengths employed has been tested by the run of the object ball, it is useless for the billiard student who hopes—with a reasonable amount of practice and within a reasonable time—to excel, to commence middle pocket in-off play.
To ensure a continuance of middle-pocket red ball play four essentials must be borne in mind. These are (1) and foremost, the required direction to be imparted to the red ball; (2) the contact to be made to ensure such direction; (3) the ability accurately to drive the cue ball along the line of intended aim; and (4) the correct variation of strength that is necessary in order to bring the red ball back or gently to guide it to a playable position.
The strength must, of course, be adapted to the nature of the contact. Fuller contacts require less strength and finer contacts more.
A gentle full contact sends an object ball a table length, whereas a grazing contact might only move it an inch.
Let it be imagined now that the red ball instead of being on a line drawn from the central 23-inch point already described to the centre of either middle pocket—from any part of which for most of its length a half-ball contact from the D sends the object ball up and down the table exactly parallel with the side cushion—is a little below or above such line.
If it be below, the aim must evidently be fuller than half-ball or the object ball will be directed out of the parallel line and cut too much across the table. If it be above, the aim must be finer than half, or the object ball will be driven towards the side cushion.
Exactly how the required aiming point may in all cases be instantly ascertained will form the subject of the next article.