By 1868 the thickness of slate beds had started to increase with Burroughes & Watts tables using slates between 1" - 1½" thick and either four of five in number. Even so, problems were still being encountered with sag, and a distinct rumbling noise as the ball rolled across the surface. From this date slate beds began to be produced in thicker sections in an attempt to overcome these problems. High quality tables now began to have slates from 1½" - 2" thick, and some examples of 2½" are known. As a direct result of the increased weight, the number of sections used was now always five. The increased weight of the slate also meant that a more substantial wooden structure was required to provide the support. The number of legs was now never less than eight, and for the 2½" slates these were of massive proportions. After much trial and error, an optimum thickness of 1¾" was eventually accepted as standard.
The first reference to gas lighting of a professional billiard match occurred in 1868. The invention of the gas "mantle" around this time improved illumination even further.
1868 also saw a major development in the game when American John Wesley Hyatt from New York, developed the composite billiard ball made from Cellulose Nitrate Camphor & ground animal bone. Hyatt's formula was patented as "Celluloid" and was used for a wide range of products from piano keys to false teeth. This was the first "composition" billiard ball to go into commercial production and it was made by Hyatt's company, the Albany Ball Co. The early formula was rather unstable and had an unfortunate tendency to create a mild explosion if struck too hard. The balls would also pick up dirt very easily and did not have the same elasticity of ivories.
With no common standard, the positioning of the spots on a billiard table was not an exact science with variations occurring from table to table. The position of the billiard spot was usually 12½" - 12¾" from the top cushion (currently 12¾") and the "D" would be 9½" - 10" in radius. (currently 11½")