operate under light, heavy, or varying loads while maintaining high velocity and constant speed. While the engine was loosely based on existing steam engines, keeping the simple piston-flywheel design, the majority of these features were brought about by the engine's unique valves and valve gears. Unlike most engines employed during the era that used mainly slide-valve gears, Corliss created his own system that used a wrist plate to control a number of different valves. Each cylinder was equipped with four valves, with exhaust and inlet valves at both ends of the cylinder. Through a precisely tuned series of events opening and closing these valves, steam is admitted and released at a precise rate, allowing for linear piston motion. This provided the engine's most notable feature, the automatic variable cut-off mechanism. This mechanism is what allowed the engine to maintain a set speed in response to varying loads without losing efficiency, stalling, or being damaged. Using a series of cam gears, which could adjust valve timing (essentially acting as a throttle), the engine's speed and horsepower was adjusted. This proved extremely useful for most of the engine's applications. In the textile industry, it allowed for production at much higher speeds while lowering the likelihood that threads would break. In metallurgy, the extreme and abrupt variations of load experienced in rolling mills were also countered by the technology. These examples demonstrate that the Corliss engine was able to lead to much higher rates of production, while preventing costly damages to machinery and materials. It was referred to as “the most perfect regulation of speed.” Corliss kept a detailed record of the production, collective horsepower, and sales of his engines up until the patent expired. He did this for a number of reasons, including tracking those who infringed on the patent rights, maintenance and upgrade details, and especially as data used to extend the patent. With this data, a more clear understanding of the engine's influence is provided. By 1869, nearly 1200 engines had been sold, totaling 118,500 horsepower. Another estimated 60,000 horsepower was being utilized by engines that were created by manufacturers infringing on Corliss's patent, bringing the total horsepower to roughly 180,000. This relatively small number of engines produced 15% of the United States’ total 1.2 million horsepower. The mean horsepower for all Corliss engines in 1870 was 100, while the mean for all steam engines (including Corliss engines) was 30.