The question of the relative throw-off angles of ivory, crystalate, and bonzoline balls has, since the introduction of composition balls, been one regarding which there has been much controversy, but nothing definite regarding it appears to have been arrived at.
The opinion most commonly accepted appears to be that the crystalate throws off at a wider angle than the ivory, and the bonzoline at a still wider angle than the crystalate.
Also that the ivory balls are the more elastic and faster, with the crystalate and bonzoline about equal in these respects.
The following are the facts regarding them as found under test experiments. To avoid misunderstanding, I premise that I have no financial interest of any sort in any of them, and started completely without bias or predilection for one more than another. It is desirable that the manner in which my experiments were carried out should be shortly described to permit readers to judge of their value.
The object ball angles of all three kinds at the various divisions (and, indeed, of every kind of ball, no matter of what it is composed, provided the balls are equal spheres travelling on a horizontal plane) are exactly the same under all conditions. Their values are set out in "Practical Science of Billiards." Cue ball angles, however, vary with the manner and strength with which they are struck. Consequently, in order to ascertain the relative values of cue ball angles, it is necessary that the cue ball should always be impelled in a precisely similar manner in every case. And it must be beyond doubt that this is so. This, if not impossible, 5s exceedingly difficult to attain, if personality is allowed to come into play. Consequently it is a necessity that there should be a mechanical means of propelling the cue ball that will never vary.
This was obtained by means of the use of a movable inclined plane of fixed height, length, and slope, down which the ball was allowed to roll in a bottomless groove, and consequently it always started with practically exactly the same velocity and did not carry any side or screw.
This is proved by the ball when allowed to run up and down the table, without coming into contact with another ball, always coming to rest at almost precisely the same spot.
The next necessity is to be able to make the cue ball travel in any exact required direction, and to be able to make it strike the object ball at exact desired points or divisions.
It is unnecessary to point out that these requirements would test the powers of even the most skilled professional, particularly when it has to be done thousands of times, and there would still remain the doubt whether there had been variations in the manner of striking.
The third necessity is to be able to ascertain the exact spot or division at which the object ball has been struck, and, if desired, to be able to repeat the stroke as often as necessary for verification.
And the fourth necessity is to be able to measure the angle that the direction of the cue ball, after impact, makes with its direction before impact, measuring from the point of divergence, which is not the position of the object ball, and is consequently an unknown spot.
The inclined plane, to which, in the form I have constructed it, I have given the name of the "billiard gun," supplies the means of complying with the first two "necessities," and the "pointer" described in the "Practical Science of Billiards" supplies the means of carrying out the third and fourth, and it is with the aid of these two appliances that the experiments have been carried out.
The results given may be relied on, as they have all been repeatedly verified, and the "pointer" supplies the means of testing them to those who desire to do so.
The assumption is made that the objective of the cue ball is 4ft. from the point of divergence. The effect on the angles of variations in this respect is explained in the chapter on "Rebound" in "Practical Science of Billiards," and the matter is only referred to here to complete the full data of the experiments.
All three kinds of balls have been tested at all the standard divisions of the balls, viz., 1/8, ¼, 3/8, ½, 5/8, ¾ and 7/8, and the balls with which the experiments were carried out were all absolutely new and previously unused so that no question can be raised regarding the balls being untrue or uncertain through wear, etc.
Angles.
We can now come to the actual angles of the balls as found by experiment in the manner described above, and they are as follows:—
Cue Half-ball Angles at No. 2 strength (measured from a point in the path of the cue ball 4ft. distant from the point of divergence):
IVORY, 33°30'.
BONZOLINE, 35°.
CRYSTALATE, 36°35'.
It will be observed that the bonzoline, instead of throwing off at a wider angle than the crystalate, has a finer angle, and lies about midway between the ivory and crystalate.
The strength (for definitions of strength see "Practical Science of Billiards") at which all the balls were delivered is No. 2 strength. No. 2 strength is rather faster than the strength with which the majority of strokes are played, which are mostly in the vicinity of 1 to 13, but the distances and nature of the strokes were such that anything less than No. 2 strength would have been insufficient for many of them, and it was necessary to adhere to a fixed strength throughout.
As the strength decreases or increases, the angles for all three natures of balls, will slightly decrease or increase, but they will retain very nearly the same relative proportion.
The angles of all three kinds of balls at all the recognised divisions are given in the following table:—
Cue Ball Angles of Ivory, Bonzoline, and Crystalate Balls when struck with No. 2 strength, without side or screw, when the objective of the Cue Ball is 4ft. distant from the Object Ball.
| Divisions | Ivory | Bonzoline | Crystalate |
| 1/8 | 16°28' | 17°54' | 19°34' |
| 1/4 | 27°25' | 29°20' | 31°27' |
| 3/8 | 32°32' | 34°19' | 36°35' |
| 1/2 | 33°30' | 35° | 36°35' |
| 5/8 | 31°32' | 32°44' | 34°2' |
| 3/4 | 27°10' | 28°3' | 28°59' |
| 7/8 | 19°54' | 20°29' | 21°5' |
When changing from ivory to bonzoline, as from bonzoline to crystalate, or vice-versa, strokes would not be missed, generally speaking, though without doubt the difference should be borne in mind, particularly in longish shots. As between ivory and crystalate, the difference is more marked, and would require slight allowance for.
If players desire to ascertain to what extent these differences affect the placing of the cueball in the baulk semi-circle for half-ball strokes, which is the most common practical way of judging half-ball angles, they can do so in half a minute with the aid of the "pointer" (using case F, page 130, where full detail of the simple procedure necessary is given). They will probably be surprised to find how very much nearer together the true positions are than they possibly judged them.
Elasticity.—The coefficients of elasticity of the three balls are as follows:—
Here, which is also contrary to the general belief, the composition balls are more elastic than the ivory, the crystalate being the most elastic of the three.
This is also evident from the angles. The cue half-ball angle of a totally inelastic ball would be 19 degs. 6 mins., and the cue half-ball angle of a perfectly elastic one would be 60 degs. Whether greater elasticity is an advantage may be a matter of opinion, but its effect is to make the throw-off angle wider.
Weights.—In each case the three balls of the same kind were practically of the same weight and size. The weights of the balls were as follows:—
The crystalate were 16/64ths = ¼ oz. heavier than the ivory, and the bonzoline were 27/64ths, or more than 3/8 oz., heavier than the ivory, and 11/64ths, or more than 1/8 oz., heavier than the crystalate.
Size—The respective diameters of the balls were as follows:—
The recognised standard size of a billiard ball is 2 1/16in.
Why the composition balls are made larger I am unable to suggest. If they were made exactly 2 1/16in. they would more nearly approach in weight the ivory balls, which they aim to as nearly reproduce as possible.
Price, appearance, wear, country of manufacture, etc., are matters outside the province of my experiments, and most readers are acquainted with the facts regarding these.
C. M. WESTERN, Col.