116 ANNUAL OF SCIENTIFIC DISCOVERY. 



of the propellers being hoisted out of water, and is somewhat dif- 

 ferent from any hitherto essayed. The wings of this propeller are 

 arranged in pairs, and are each of no greater width than the dead 

 wood of the vessel in which the propeller is located. The first pair, 

 if there be six wings, is attached to a hollow shaft ; the second pair is 

 fastened to another hollow shaft, concentric with and inside of the 

 first-named one ; and the third pair is secured to a solid shaft, also 

 concentric to the first and located within the second hollow shaft ; 

 each pair lies a little behind the former in the direction of the length 

 of the vessel, and their shafts are fitted with gearing and clamps, 

 or their equivalents, in such a manner that the various pairs of 

 propellers can be made to alter their angular distance with respect 

 to each other, or be clamped at any specified relative position. 

 This gearing is within the vessel, and by means of it the various 

 blades are, when the propeller is to be used, spread around the 

 whole periphery of a circle, so that each acts in turn and in the 

 same position as in an ordinary propeller, where the wings have 

 no motion with respect to each other. When, however, the propel- 

 ler is no longer to be used, and sail is to be employed, then, by 

 means of the gearing, the blades are revolved so as to fold the 

 one behind the other, like the leaves of a shut fan, and the whole 

 set are turned so that they lie in the line of, and are covered by, the 

 dead wood, thus offering little or no resistance to the progress of the 

 vessel. The engine is connected to the outer shaft in such a manner 

 that it drives the whole of the shafts, without altering their angular 

 position with respect to each other ; the motion to produce this latter 

 result being entirely independent of the former. 



Improvement in Canal Boats. A method of fitting canal boats 

 to be used for the conveyance of coal, &c., appears to present features 

 of utility, and will probably lead to a material saving in the discharge 

 of cargoes of that article. Beams are secured along the inside of the 

 boat's ceiling for its whole length from stem to stern, forming a species 

 of continuous bracket round the interior of the vessel, at a distance 

 of some two or three feet from the bottom. Along the bottom are 

 laid rails, upon which a small car may be moved, and immediately 

 over the car's top, from beam to beam, crosswise of the boat, are laid 

 planks, which form the cargo deck, on which the coal, &c., are loaded. 

 In the process of unloading, one plank at a time is lifted up by crow- 

 bars, and the cargo runs by degrees into the car underneath. This 

 car, when full, is run along the track until free of the floor and then 

 hoisted out as a bucket and emptied, replaced, run back, and filled 

 again. All shovelling of the coal is saved by this contrivance ; and it 

 will probably be adopted in boats which, after their passage through 

 canals, discharge their coal for further transport into the hold of sea- 

 going vessels. 



Improvement in Harpoons. - - A harpoon, which forces the point 

 deeper and deeper into the whale as he draws the boat after him, has 

 been invented and patented. In this contrivance the ilukes are 

 hinged, and so arranged that they can be latched to the point, or can 



