The more efficient generator.
Innovation is not usually invention. The compound steam engine is a perfect example of how smart thinking can make a good thing even better. In this case, the thinker was Fredericton, New Brunswick, native Benjamin Tibbets.
The problem he considered was the wastage of heated steam in engines. Before Benjamin put his mind to the problem, steam engines required vast amounts of carbon fuel to produce vapour, which was then used briefly to produce power and subsequently exhausted into the atmosphere. In 1853, he built a new kind of steam engine incorporating a reservoir and a second cylinder. These two features enabled the engine to take the steam discharged from the main high-pressure cylinder and put it to further use as low-pressure steam. The result was a more efficient power generator that used much less fuel per unit of usable energy.
The concept, refined by others, was subsequently incorporated into all steam engines with immediate impact. The additional power made developments such as long-distance train travel a reality at last.