Opening The Game.
In respect to ball 2 the matter is different; it cannot, as has already been shown, be struck save on the line C C′ A, the height moment of reaching 2, then its position will be that of the dotted circle 1″, whose centre is C″, and P′ is the point of impact. For any stroke between full and half-ball the point of impact will lie between P and P′; between half-ball and the extreme of fineness the point of impact will lie beyond P′ in the direction of E.
Ball 2 being struck by ball 1 at P′ must travel in the direction P′ B F, the line from the point of impact passing through B the centre. There is practically no departure from this rule. Hence it follows that if it be desired that ball 2 should travel in the direction B F, say to a pocket, imagine a line from the pocket passing through the ball’s centre; this cuts the circumference at P′, which is manifestly the point which must be struck by ball 1. Where is the centre of ball 1 to be aimed at in order that P′ may be struck? Produce the imaginary line F B P′ to C″, making P′ C″ equal to B P′ or in other words equal to the radius of the ball. If the centre of ball 1, C, be aimed on C″, ball 2 must be struck at P′ and must travel in the direction required.
Pray realise that it is impossible to hit ball 2 at the point aimed at save when the stroke is full; in every other case the aim must be beyond the point of impact, and the rule above given will enable anyone to determine precisely where aim should be taken.
When a ball is struck by the cue its first impulse is to slide forward, and if there were no friction between the ball and the cloth it would do so till arrested by other causes; but as there always is this friction, the lower part of the ball is thereby retarded, and the result is the rolling or revolving motion with which all are familiar. This will be further considered when the subject of rotation is discussed, but it is mentioned here as the cause of certain effects which will be observed in some of the strokes recommended for practice. When one ball impinges on another the immediate result is a greater or lesser flattening of both surfaces at the point of impact; this is instantaneously followed by recoil,[[14]] the result of each ball reassuming its spherical form. The greater the strength of stroke the greater the flattening and the greater the recoil; the converse likewise holds good.
Further, the force or strength with which ball 1 strikes ball 2 is immediately divided on impact; if ball 2 be struck full it appears to acquire from ball 1 the whole of its energy save that due to naturally developed rotation, the result being that ball 2 travels fast whilst ball 1 remains comparatively stationary. If the distance between the two balls be very small, little rotation is acquired and ball 1 transmits its motion to ball 2 and stops on or near the spot which that ball occupied; if the distance be considerable, ball 1 acquires rotation which, overcoming the recoil on impact, causes it to travel slowly in its original direction. When impact is other than full, ball 1 parts with more or less of its force, which is transmitted to ball 2. What the one loses the other gains.
These general remarks will seem to many self-evident and superfluous; to others they may prove difficult to realise and distasteful; but students, whether beginners or those who have already acquaintance with the game, may rest assured that a careful consideration of them can do no harm and may be of much advantage; for practice is assisted by an intelligent appreciation of the behaviour of balls under certain conditions; in short, by a consideration of cause and effect.
For practice: place ball 1 on the centre of the Ｄ on the baulk-line, put ball 2 a foot up the table in the central line, play 1 full on 2 with varying strength, at first with strength to carry 2 to the top cushion; the truth of the stroke will be shown by 2 passing over all the spots in the central line and 1 following slowly in the same line for a short distance. When tolerable certainty is acquired play the same stroke harder, and if correctly struck ball 2 will return from the top cushion and meet ball 1, kiss as it is called, in the central line. The stroke can be made more difficult by placing ball 2 further up the table, say on the centre spot, and playing as before, and again by placing it on the pyramid spot. This practice, though it may seem uninteresting, is most useful; it combines and continues that recommended for one ball with that required for truth of stroke on another. It also, as will hereafter be shown, is directly useful in the matter of cannons, hence it should be assiduously practised.
Fig. 5