L. MECHANICS AND ENGINEERING. 505 



advocated by Admiral Paynter consists in placing the pro- 

 peller of a screw-steamer amidships, or nearly so ; the hull 

 of the vessel itself being cut into for that purpose in such a 

 way that the blades of the propeller in their revolution do 

 not project to any important degree on either side of the 

 hull, but do project below to an extent sufficient to take hold 

 of the water and propel the vessel. The blades are so con- 

 nected with a handle, worked by the pilot on the bridge, that 

 they may, if necessary, be presented edgewise to the water, 

 and thus have no effect in propelling the vessel, or may even 

 be reversed so as to back the vessel, the shaft of the screw 

 always maintaining: the same direction of motion. The wheel 

 which carries the blades on its circumference revolves en- 

 tirely in still water in the transverse chamber, or well, built 

 as near the centre of the ship as convenient. The bottom of 

 the vessel for about thirty feet before and abaft of this cham- 

 ber is built slightly concave, so as to enable the water to 

 have free access to the blades of the screw as they grip the 

 water. A vessel of forty feet beam could easily carry a 

 twenty-foot wheel, and the wheel works at a lower speed and 

 a less consumption of fuel in order to obtain the same results 

 as a screw. The weight of the wheel acts as a fly-wheel to 

 carry the engine over the dead points or centre, so that only 

 one engine need be used on ordinary occasions. The ar- 

 rangement here described gives a great gain, both in the 

 weight of the vessel and the storage room. No matter how 

 heavily the vessel pitches, there is nothing felt of the trouble 

 so annoying in ordinary screw-steamers known as racing. 

 The ship may roll and pitch in the roughest weather, without 

 causing the blades for an instant to lose their grip in the water, 

 or cease to exert their full power. When the wheel needs 

 to be repaired in any way, the chamber in which it moves 

 can be closed by sliding ports, the water pumped out of the 

 chamber, and the parts carefully examined while the ship is 

 under canvas. Journal IZoyal Military Institutio?i,18l 4,527. 



UTILIZATION OF WAyES AS A MOTOR POWER. 



Mr. Tower proposes a method of obtaining motive power 

 from the motion of the waves of the ocean. A boat resting: 

 upon the ocean may be supposed to be acted upon by a 

 variable vertical force, equal to the difference between the 



Y 



