The “Jump”: its Causes and Preventions.
A ball is made to “jump” by being struck hard ¼ above its centre with the cue held at an elevation of 22½°. The stroke of the cue at this elevation is resisted by the bed of the table, and the ball rebounds, leaves the table and flies through the air, the distance being regulated by the strength of stroke, which is usually “hard.” When the cue-ball reaches the object-ball or cushion, its centre is above that of the object-ball or the top surface of the cushion, causing the ball to ride over whatever it may contact with. If the force used is great the object-ball will also be made to “jump,” often causing both balls to fall to the floor. When a ball lies close under the cushion it makes necessary an elevation of the cue to about the angle for a “jump;” when this occurs the player must be very careful in making the stroke, and must sacrifice a certain quantity of strength in order to secure the carom, for should considerable force be used the ball will leave the bed of the table. When the ball lies in the open table and it is desirable to use more than “ordinary” strength, it is always better to deliver the cue ½ below centre, so as to do away with any possibility of a “jump.” The motion of the ball in being struck below centre is denoted by the arrow b, the bed of the table being j, and when contacting with the cushion at a the ball is rolling upward, and the cushion acting against it holds it down to the table.
In delivering cue on ball, it is always necessary to observe the exact fractional divergence from centre, as the slightest change may make the stroke a miss. For the fractional parts of balls, the reader is referred to the next succeeding pages.
Object-Ball.
In the object-ball all distance is measured from its central width (indicated in cut by dotted line a) to its outer edge surface, and the fractional strokes are calculated from this centre point, each divergence denoting the body resistance received by the cue-ball from the object-ball; thus with 8
8 as a full ball, ⅞ signifies ⅛ to left or right of centre as may be instructed.
The position which the object-ball may assume after being struck is unimportant, so far as that particular stroke is concerned; but in the management of the balls and the ability to leave them in a position favorable to the next play—or unfavorable to his opponent, if the player thinks it impossible to count himself—lies the strength and science of the game.
General Division of the Object-Balls.
The spots on the horizontal line through the centre diameter of the ball, are the different fractional parts at which the cue-ball may be delivered, to effect certain results. The spots are made by exact measurement, and extend from the pivot A toward either side surface. The centre A indicates a “dead full” delivery. The spots right and left of this centre show the points of impact for the cue-ball, as may be directed.
