Case-hardening.—What is case-hardening? What parts of an engine are usually case-hardened? [II. 442].

Forging.—What are the forgeable metals used in engine construction? [II. 442].

Welding.—What is welding? [II. 442].

Metal expansion.—What metals used in engine construction expand by heat, and what allowances are made in the construction on this account? [II. 442].

Composition of iron and steel.—What is the difference in the composition of cast iron and steel? [II. 442].

Marine piston.—Describe a marine engine piston. [II. 442].

Drain cocks.—What are cylinder drain cocks? [II. 442].

Link motion.—What is a link motion? What is a link motion used for? [II. 443].

Expansion valve.—What is a separate expansion valve? [II. 443].

Top cylinders.—What are the small cylinders on top of the steam chests used for? [II. 443].