14 ANNUAL OF SCIENTIFIC DISCOVERY. 



Four of these propellers have already been made and brought into use ; 

 and, as a proof of the high estimation in which they are held, it may 

 be stated that the Lords of the Admiralty have ordered her Majes- 

 ty's yacht, the Fairy, the swiftest screw-vessel afloat, to be fitted out 

 with one of them in preference to the rigid screw. Sheffield {Eng- 

 land) Times. 



PROPELLER FOR CANALS. 



ANOTHER invention for adapting steam to canal navigation has been 

 brought out by Mr. O' Regan. The boat resembles in size, shape, 

 and general appearance, the ordinary fly-boats employed on our canals, 

 which have hitherto been worked by horses only. The steam is gen- 

 erated by a vertical tubular boiler, to which an engine of six horse- 

 power is attached. The cylinder is five and five eighths inches in diam- 

 eter and often and a half inches stroke, the pressure being fifty pounds 

 to the square inch. A screw, two feet four inches in diameter, and 

 consisting of two arms, is mounted in the stern, immediately behind 

 the rudder ; attached to which is a horizontal axle of considerable 

 length, passing longitudinally through the bottom of the boat, as near 

 the keel as practicable. A driving band, worked by a large wheel, 

 causes this axle to revolve with great rapidity, ninety revolutions 

 being produced in each minute, and four times as many revolutions of 

 the screw. The chief peculiarity is the position of the axle and screw, 

 the former of these being placed extremely low down, so as to enable 

 the screw to work at a considerable depth in the fluid, an arrangement 

 which materially augments the propelling power, and at the same 

 time causes as little commotion as possible in the upper stratum of the 

 water. This boat has been propelled at the rate of five miles per 

 hour. The space occupied by the engine is only three feet four inches 

 by two feet six inches, and the width of the boiler*is about three feet. 

 The engine consumes eight hundred weight of coal per day, and the 

 entire cost of the propelling, inclusive of fuel and the wages of the 

 enginemen and firemen, is, according to Mr. 0' Regan's estimate, only 

 4d. a mile, while the cost per mile, where the motive power is sup- 

 plied by horses, is no less than Is. ( Jd. Saunders' News-Letter- 



A steamboat intended to accomplish the same purpose has arrived 

 at Trenton, New Jersey, and is described in the State Gazette. She 

 has but one large paddle-wheel, which is placed in the centre of the 

 boat, and the paddle-boxes are so constructed as to hold the water 

 when they enter it, and prevent it from escaping sideways. The wa- 

 ter is thus drawn from the front and sides of the boat and thrown out 

 at the stern, so that the boat makes no swell. She has one boiler and 

 two engines, and can, it is said, tow boats containing one thousand 

 tons of coal at the rate of three miles an hour. 



PERPENDICULAR AND RADIAL PADDLE-WHEELS. 



AT the close of an elaborate investigation, in the Journal of the 

 Franklin Institute, of the comparative merits of the perpendicular and 



