I 



TRANSACTIONS OF THE SECTIONS. 223 



and tlie long' shaft is a soiu-co of endless trouljle. It is with the hope to obviate 

 these evils that the new propeller is proposed. This propeller is, in fact, an attempt 

 to transfer the action of the screw to the middle of the ship. Prior attempts have 

 been made to do this and have failed, not on their intrinsic merits, but inciden- 

 tally through weakening the ship or requiring special and peculiar forms of ships. 



Whatever demerits the proposed propeller may have, it must necessarily have 

 the following merits : — 



1. It is in the middle of the ship, and its action is not affected by pitching. 



2. Its action cannot be affected by the rolling of the ship. 



3. It will not interfere with the action of the rudder. 



4. It will not interfere with the sailing-qualities of the ship. 



5. It can be applied to ships of any form of section. 



G. Its immersion will not be much altered by the lading of the ship. 



7. For sailing, the propeller or the blades can be easily removed. 



8. If applied to rams, they could strike with either end. 



The experiments which have been made with tlie model, which is 5 feet long, 

 have been very successful. It vv-ill steam at about two miles an hour, and it appears 

 to go quite as well in rough Vv'ater as it does in smooth. It goes quite straight 

 without any rudder, and does not heel over from the effect of the propeller. 



Description of the Propeller. — The plates which act on the water are fastened 

 obliquely on to a flat endless chain, which is made so that it cannot be twisted. This 

 chain passes round the middle of the ship, or it may pass across under the deck 

 and then through the sides and down outside, and so mider the bottom. In this 

 way the chain wUl uuder-gird the ship in her middle, and the blades will act on all 

 the water which comes within their length of the bottom or sides amidship. The 

 draft of the ship will be increased by the length of the blades, which will be about 

 one-seventh the entire draft. The chain is kept in its position by drums, which 

 project a short distance beyond the skia of the ship. These drums must be so 

 incased as to keep the water from getting into the ship. The chain is connected 

 with the engines by means of one of these di'ums. Flanges on the di'ums prevent 

 the chain working off them. In order to ascertain as far as possible the compara- 

 tive merits of this propeller and the screw, one was designed for a large ship, the 

 drawings of which are given in Scott Eussell's ' Naval Architecture,' the size of all 

 the parts being very carefidly calculated, and then it was compared with the screw. 

 The residts of the comparison are given in the adjoining Table. 



Dimensions of the SJiip taken from Scott RusseWs ' Naval Architecture,^ 



Length on load water-line 314 ft. 6 in. 



Breadth, extreme 42 ;; 3 » 



Depth at side 31 „ 3 „ 



Tonnage, builder's measurement 2780 tons 



Draft when laden 22 ft. 



Nominal horse-power 600 



Indicated „ 2500 



Speed in miles per hour 13'7-'5 



Dimensions of existing Machinertj. 



Length of screw-shnft Ill ft. 



Diameter of screw-shaft 1 ft. C in. 



Pitch of screw 34 ft. 



Number of blades .3 



Diameter of screw 19 ft. 



Number of revolutions per minute 46 



Slip in miles jier hour 4 



Approximate vcight of screio and screio-shnft . . tjQ tons 

 Friction arising from thrust-blocks is equiva- 1 r, i- + 



lent to an additional thrust of / ^"-^ ^°^ 



Ditto weight of shaft and screw 05 „ 



Thrust of ship 23 tons 



Totalincrease of thrust equivalent to friction ., '75 ton 



