Of course it cannot be mathematically correct at all distances, but it is near enough for practical purposes, and will help to train the eye to estimate half-ball angles.
Fig. 40
The two lines marked upon the upper surface of the instrument, if produced through the angle A, will give the direction taken by the object ball after collision, according as the shot is played from B or C.
An Outside Billiard-room
CHAPTER III
ELEMENTARY: ONE-BALL PRACTICE
Before commencing the manual of instruction in billiards, it is desirable to address a few words of advice to the beginner, and to explain some of the technical terms used. Others will be described in future chapters.
It is clear that before playing, the room must be entered; and hence we commence with the mode of doing so. The operation seems so simple as to be too trivial for notice; but, far from that, there is nothing short of actual play which shows more clearly the difference between a well-trained, well-mannered player and a novice or a careless and discourteous visitor. The door of a room should always be approached quietly, for the table may be occupied; if it be so, wait for the stroke. When the stroke is played, open the door quietly, and walk straight to a seat. Avoid everything likely to distract the attention of the players from their game, and recollect that for the time being the room, its light, fire, and so forth, belong to them. Persons who smoke should wait for the stroke before scratching a match, and when extinguishing it should not do so by waving it before the eyes of the player. In short, ordinary courtesy is nowhere more important than in the billiard-room, for if men can play, their nerve and attention are strained; interruption may prove fatal to the chance of one of them, and is sure to be resented, even though it may pass without remark.
In the previous chapter the terms employed respecting the table and implements have been detailed; these are now supplemented by others in common use during play.