Better than Ivory! Courtesy of the Internet Archive

Bonzoline is an old ivory replacement used for billiard balls mentioned in "What Jorkens Has To Put Up With", where it forms a kind of punchline.

But we were discussing billiards today, and debating whether bonzoline balls or the old ivory kind were the better. I will not record the discussion, for it has nothing to do with Jorkens, but it may interest my readers to hear that it was held at the Billiards Club that the bonzoline ball was unique among modern substitutes, in being better than the old genuine article.

There's not much about bonzoline in Google - mostly blank entries in online dictionaries - but I did manage to find this bit on the introduction of the material:

By 1893 Hyatt had overcome the problems with the composition billiard ball and his new formula was marketed under the name of "Bonzoline". The Bonzoline Manufacturing Co. Ltd was established in England to sell these balls. However, the reputation of his earlier attempt remained linked to the new ball and initially there was some resistance from the public. Although a source of major controversy at the time, in hindsight there was little doubt that the new ball was superior in all respects to ivory, having more accurate manufacturing tolerances and a consistent density which ensured true running. Although slightly heavier [c.5½oz.] than ivory [c.5oz.] they threw at a wider angle. Whilst the composition ball became increasingly popular at an amateur level, it failed to displace ivories in England as long as they were used by professionals and endorsed by the Billiard Association. This attitude from the hierarchy of the game persisted well into the 20th century when it was eventually overtaken by the groundswell of amateurs who had never played with ivories due to their scarcity and expense. In the colonies however (Australia, New Zealand, South Africa, India) the composition ball was used almost exclusively since their earliest introduction to those countries.

The "problems" here are only explained in the 1860s section - early synthetic balls were made out of celluloid, which was brittle rather than springy and gained a reputation for exploding - while that wasn't true (production involves dangerous explosives, but celluloid can only burn slowly), it still had a negative effect on adoption. Bonzoline was similar to celluloid but also included crushed animal bones that made it more similar to ivory. Ψ