212              LECTURE XX.

                          LECTURE XX. - QUESTIONS.

1. Sketch and describe by an index of parts a side and an end view of
the general arrangement of diagonal direct-acting engines, as fitted into a
river passenger steamer, including the boiler.

2. Why are compound-diagonal direct-acting engines preferred to
oscillating or other kinds of engines for shallow river paddle-wheel
steamers?

3. Sketch and describe by an index of parts, side views and a plan of a
compound direct-acting diagonal engine.

4. Sketch and describe by an index of parts, Joy's valve gear, pointing
out its advantages and disadvantages as compared with eccentrics and
link-motion.

5. Steamer main shafts often break, or their bearings give trouble by
heating, account for this, and describe a plan or plans for alleviating this
evil.

6. Sketch and describe a simple radial paddle-wheel. For what reasons
has this form of wheel been abandoned?

7. Sketch and describe, by an index of parts, a modern feathering float
paddle-wheel. What advantages has it over the older form of paddle-
wheel?

8. Describe how you would design and construct the arms, floats, and
feathering arrangements for a paddle-wheel.