MECHANICS AND USEFUL ARTS. 31 



and the late Dr. Robinson, of Edinburgh, undertook a series of experi- 

 ments, with the view of ascertaining the form which would enable a 

 vessel to move most quickly through the water. These experiments 

 lasted for years, and established a set of facts which were reduced into 

 new rules, the majority of which were decidedly the reverse of the old 

 rules in ship-building. They began by upsetting the old rule that the 

 length of a vessel should be four tunes its breadth, as they found that 

 the greater the speed required, the greater should be the length, and 

 that the vessel should be built merely of the breadth necessary to stow 

 the requisite cargo. The second great improvement was, that the 

 greatest width of the water line, instead of being before the middle, 

 should be qbqft the middle of the vessel in fact, two fifths from the 

 stern and three fifths from the bow. The next great improvement was, 

 substituting for broad, bluff, or cod's-head bow, hollow water lines, 

 called wave-lines, from their particular form ; and, also, instead of the 

 old fine run abaft and cutting it away, you might, with advantage, 

 have a fuller line abaft, provided it was fine under the water. By 

 these improvements the form of the old vessel was nearly reversed. All 

 the fast steamboats, accomplishing from 16 to 17 miles an hour, are 

 built on this principle. English Journal. 



FAN PADDLE-WHEEL. 



MR. LEE STEPHENS, of England, contributed to the Great Exhibition 

 a model of a new, and, it is thought, effective system of surface propul- 

 sion for steamers, which has been denominated the " fan paddle- 

 wheel." It consists of a series of blades, or segments, connected 

 together from their common centre (the boss which attaches them to 

 the shaft) to their common periphery, in such a manner as to constitute 

 a complete rotatory fan. Each blade is an isosceles triangle, every two 

 blades forming at their outer extremities two sides of an equilateral 

 triangle, occupying the full width of the paddle-box, the united action 

 of the whole being necessarily continuous, although the blades, alter- 

 nately, compress or divide the water right and left, yet entering and 

 leaving it so obliquely as to avoid unpropulsive disturbance, or any lift- 

 ing of back-water ; of course, the propulsive effect is precisely the 

 same forward or backward. Without a diagram we cannot more par- 

 ticularly explain the invention, but we venture to believe that none of 

 our readers can fail to comprehend its ingenious simplicity, when they 

 keep in mind the fact that the constructive principle may be cor- 

 rectly defined as that of a rotatory fan. It is applicable to ail surface 

 propelled steamers, of whatever size ; and its advantages are 

 simplicity, strength, and economy of construction, even compared 

 with the common paddle-wheel ; avoidance of vibration by continuity, 

 and of back-water by peculiarity of action ; decreased retarda- 

 tion when deeply immersed ; and increased speed with the same 

 amount of power, consequent upon the saving in that power by conti- 

 nuity of action, and by the entrance and egress of each segment of the 

 fan obliquely, instead of horizontally. In action each segment assim- 

 ilates to the motion of a fish's fin, or to that of a scull or oar, and the 



