While most of us are limited to the visible spectrum, people with a condition called aphakia possess ultraviolet vision. Aphakia is the lack of a lens, due to surgical removal for cataracts or congenital defects.
A railroad lantern and a railroad lamp are two different things. Lanterns were designed to be portable (i.e. carried) and were basically globes surrounded by a metal frame with a fuel source. When you think of a railroad worker swinging a signal, think lantern.
What is a heat engine? An engine is a machine that turns the energy locked in fuel into force and motion. Coal is no obvious use to anyone: it's dirty, old, rocky stuff buried underground. Burn it in an engine, however, and you can release the energy it contains to power factory machines, cars, boats, or locomotives. The same is true of other fuels such as natural gas, gasoline, wood, and peat. Since engines work by burning fuels to release heat, they're sometimes called heat engines.