cutter of a type common on the Thames and drove two paddle wheels. Its speed was claimed at 7-8 mph (6 knots). The gas used was water gas, i.e. the mixture of hydrogen and carbon monoxide obtained by passing water over white hot coke. The benefit of using water gas generated from steam rather than the steam itself was said to be a factor of 30, plus the weight of the engine was said to be 600 pounds compared to 2 to 3 tons for an equivalent steam engine. This experiment had been funded by the Canal Gas Engine Company, who met the same day and after discussing the experiments in spite of acknowledging the success of the trial decided to wind up the company rather than raise further funds. In 1832 Brown demonstrated three of his engines of different types and construction at his premises at Eagle Lodge, Old Brompton. All three engines were in operation and one was of the same type as had been operating successfully on the Croydon Canal raising water from a lower to a higher level since June 1830. The economics of the Croydon Canal engine were interesting as the gas it consumed was made by turning coal into coke. The value of the resulting coke and coal tar by-products of making the gas substantially exceeded the cost of the coal, ground rent, repairs etc, so the gas vacuum engine made a profit of over £100 a year before considering the useful work it was doing. Unfortunately the economics of the Croydon Canal were not so robust and it closed in 1836. The gas vacuum engine complete with gasometer in situ on Croydon Common was auctioned as a going concern in 1837. It was described as able to lift water a height of 11 feet at a rate of 2000 gallons per minute. The reports of an 1834 court case reveal that Brown and Company had been contracted to build a large gas vacuum engine to pump the fens at Soham. This engine had been designed to pump 7805 gallons of water per minute, lifting water 14 feet at 14 strokes per minute. It fell short of specification and only delivered two thirds of its rated horsepower, with a lift of 10 feet 6 inches. The gas vacuum engine was eventually to become a commercial success. In 1853-1854 Eugenio Barsanti and Felice Matteucci invented