"burnt in a furnace surrounded by water created ; steam confined in a cylinder pushed a , and linked to wheels by rods that turned the straight thrust of the piston into rotatory motion, the moved and worked. The idea that hordes of people and commodities could be carried at such shockingly powerful speeds by a sort of articulated kettle, in which the water could never be allowed to fall below the top of the furnace or there would be an explosion, seemed amazing to me. What made it all so different from today's s, which run at set speeds, was the need to be aware at every moment of the perilous balance of fire and water, which also gave the possibility of going a little faster if the engineman was good, or of disaster if he was incompetent."