Short answers, pulled from the story.
Dictionary.com defines an engine as any device that converts another form of energy into mechanical energy so as to produce motion. Available energy sources include potential energy, heat energy, chemical energy, electric potential and nuclear energy.
Hero of Alexandria created wind and steam powered machines in the 1st century AD including the Aeolipile. These early systems used aqueducts, dams, sluices, and gear trains made of wood and metal.
James Watt developed his design sporadically from 1763 to 1775 improving upon Thomas Newcomen's 1712 engine. Matthew Boulton served as business partner helping make the design synonymous with steam engines.
Karl Benz received a patent in 1896 for his horizontally opposed pistons design. These flat or boxer engines automatically balanced momentum since corresponding pistons moved simultaneously in horizontal cylinders.
Exhaust gas from spark ignition engines contains nitrogen 70 to 75 percent water vapor 10 to 12 percent carbon dioxide 10 to 13.5 percent. Carbon monoxide ranges from 0.1 to 6 percent while unburnt hydrocarbons reach 0.5 to 1 percent.