A process is claimed for the production of substantial amounts of ethylene and other hydrocarbon compounds, such as benzene from coal. Coal is reacted with methane at a temperature in the approximate range of 500/sup 0/C to 1100/sup 0/C at a partial pressure less than about 200 psig for a period of less than 10 seconds, and preferably at a temperature of approximately 850/sup 0/C, and a partial pressure of 50 psig for a period of approximately 2 seconds. Ethylene and other hydrocarbon compounds may be separated from the product stream so produced, and the methane recycled for further production of ethylene. In another embodiment, other compounds produced, such as by-product tars, may be burned to heat the recycled methane.

A ball mounting fixture for a roundness gage is disclosed. The fixture includes a pair of chuck assemblies oriented substantially transversely with respect to one another and mounted on a common base. Each chuck assembly preferably includes a rotary stage and a wobble plate affixed thereto. A ball chuck affixed to each wobble plate is operable to selectively support a ball to be measured for roundness, with the wobble plate permitting the ball chuck to be tilted to center the ball on the axis of rotation of the rotary stage. In a preferred embodiment, each chuck assembly includes a vacuum chuck operable to selectively support the ball to be measured for roundness. The mounting fixture enables a series of roundness measurements to be taken with a conventional rotating gagehead roundness instrument, which measurements can be utilized to determine the sphericity of the ball.