The subject of compensation is very interesting, and its proper use is one of the refinements of play. Certain elementary forms will be described, but the application of the principle to the execution of strokes must be left to the intelligence of the player; and this may with safety and a clear conscience be done, for the less ambitious and clever player will not concern himself with the question.
Perhaps the simplest form with which ordinary amateurs are familiar is that whereby the angle between the paths of ball 1 before and after impact with ball 2 is diminished or enlarged by side which compensates for strength. Thus, taking plain losing hazards of the simplest type (Diagram IV. p. [157]), side may be substituted for strength, and the angle of deviation altered so that with the strength prescribed for the first hazard the second and even the third hazard may be made. Similarly, reverse side will compensate for fine striking; it will, in other words, decrease the angle of deviation.
These remarks of course apply equally to cannons, and with them also compensation is used in order to control the movement of ball 2. Without a knowledge of the motions which may be communicated to a ball by a cue, and the skill to apportion them at will, no long break can be continued. For the power to leave ball 2 in a certain position or direction is often a necessity; hence, whilst the actual stroke is made, that ball must be struck sometimes on one spot, sometimes on another, and therefore compensation must be supplied for the variation of aim.
Fig. 3
Consider a right-angle screw stroke.
In fig. 3 let 1, 2, 3 be the balls; if played half-ball, R will be the point of impact between balls 1 and 2, therefore the path of ball 2 will be in the direction R P. But suppose for some reason it is desired that ball 2 should travel towards P′. Then impact must be at R′, and, this being fuller than before, ball 2 will travel faster and ball 1 slower, if the strength of the two strokes is the same. But as ball 2 is struck fuller, less screw is required, and therefore ball 1 need not be hit so low. Here the additional fulness on ball 2 is compensated for by a diminution of screw, and the cannon is made; were the screw kept the same as that necessary when impact was at R, ball 1 would return to some such position as 1′, and the cannon would be missed.
Again, suppose that it is wished to send ball 2 towards P″; R″ must be the point of impact, and that makes the stroke so fine that ball 2 will travel much more slowly, and ball 1 as much faster; hence, to get the cannon, ball 1 must be struck extremely low to compensate for the loss of recoil occasioned by taking ball 2 so fine. So, if it be desired to make ball 2 in this case travel as far as before, additional strength must be used to compensate for the fineness of the stroke. This example shows the principles involved; working them out and applying them correctly to particular strokes is a matter of practice and experience, without which theoretical knowledge is useless or nearly so for purposes of play.
Another common illustration of the principle of compensation is the drag stroke, which was explained at p. [197]. As the ball is hit more and more below the centre according to the length of the path to be travelled, so must greater strength be used to compensate for the loss of naturally developed rotation; and, conversely, when that rotation is too powerful, or when there is special need for accuracy of path, or necessity for diminishing the travel after impact with ball 2, compensation is given in the form of retrograde rotation by striking ball 1 below the centre.
It is hardly necessary to give more examples, the great matter being to direct attention to the general principles which govern the conversion of strokes, and to make the player inquire why he attempts a stroke in a certain way. When he begins to do this and can solve such questions satisfactorily, the power will soon follow to realise at sight the compensations which he must apply to each stroke as it occurs in order to continue a successful break; and then, as in other matters affecting us, the value of calm sound judgment becomes apparent.