century, after the expiration of the Boulton & Watt patent in 1800, the steam engine underwent great increases in power due to the use of higher-pressure steam, which Watt had always avoided because of the danger of exploding boilers, which were in a very primitive state of development. Until about 1800, the most common pattern of steam engine was the beam engine, built as an integral part of a stone or brick engine-house, but soon various patterns of self-contained portative engines (readily removable, but not on wheels) were developed, such as the table engine. Further decrease in size due to use of higher pressure came towards the end of the 18th century when Cornish engineer Richard Trevithick, and American engineer Oliver Evans, independently began to construct higher-pressure (about ) engines that exhausted into the atmosphere, although Arthur Wolf working at the Meux Brewery in London was already experimenting with higher-pressure steam in his efforts to save coal. This allowed an engine and boiler to be combined into a single unit compact and light enough to be used on mobile road and rail locomotives and steam boats. Trevithick was a man of versatile talents, and his activities were not confined to small applications. Trevithick developed his large Cornish boiler with an internal flue from about 1812. These were also employed when upgrading a number of Watt pumping engines; by this time Arthur Wolf had already produced high-pressure engines whilst working at Meux Brewery, in his efforts to improve efficiency, thus saving coal, as he had been trained by Joseph Bramah in the art of quality control, which resulted in him becoming chief engineer at Harveys of Hayle in Cornwall, by far the largest and leading manufacturer of steam engines in the world. The Cornish engine was developed in the 1810s for pumping mines in Cornwall. It was the result of using the exhaust of a high-pressure engine to power a condensing engine. The Cornish engine was notable for its relatively high efficiency. The Corliss Engine The last major improvement to the steam engine was the Corliss engine. Named after its inventor, George Henry Corliss, this stationary steam engine was introduced to the world in 1849. The engine boasted a number of desired features, including fuel efficiency (lowering cost of fuel by a third or more), low maintenance costs, 30% higher rate of power production, high thermal efficiency, and the ability to