4Ö2

MODERN STEAM PRACT1CE.

advance of the other, or, in other words, a two-bladed screw isformed in duplicate. It is advisable to cut away the sides from the

Fig. 363.—Two Propellers cast on one Boss,a, Boss. b, Double blades.

middle of the blades to the centre (as seen in Fig. 363), by whichineans the water is not churned so much, while the after blade gets

Fig. 364.—Six-bladed Feathering Propeller.a, Boss. b, Blade. c, Blade showing thickness of metal.

a better grip. In other forms six blades have been successfullyadopted. The blades are narrow and almost parallel in the front