440 Mr. Dick on a Spiral Oar. [June, 



have no doubt many very effectual plans for doing both will 

 speedily suggest themselves to every well-informed mechanic. 

 It is chiefly the principle of the oar itself to which I wish to call 

 your attention. 



The spiral oar possesses many advantages over the common 

 oar, and amongst these, Mr. Scott particularizes the following. 

 The back stroke of the common oar, which is both a loss of 

 time and of labour, is altogether avoided by the constant revo- 

 lution of the spiral oar, continually tending to give a steady and 

 unremitting progressive motion to the vessel. The ordinary oar 

 cannot be made of large dimensions without becoming altogether 

 unmanageable ; but the spiral oars may be made eight or more 

 feet in diameter, and sixteen or more feet long. Supposing the 

 wreaths of the spiral fin to be eight feet apart, it will go twice 

 round a cylindrical axis of this length. It is evident that each 

 revolution of the fin, of an oar of these dimensions and thus 

 constructed, will meet with the same quantum of resistance 

 under water, as a circular plate of eight feet diameter would 

 encounter, if similarly situated, and moving at the rate of eight 

 feet in the time of one revolution of the oar ; and that this 

 resistance will increase as the square of the velocity of the 

 oar increases. 



The machinery giving motion to these oars might be very 

 easily constructed in such a manner as to be wrought with ease 

 by men, and with this advantage, that any man, whether sailor 

 or not, could lend a useful hand in giving ivay to the vessel. 

 That these oars would be peculiarly applicable to boats is mani- 

 fest ; and there can be no doubt that with proper machinery the 

 progress of the boat would be much more rapid, and the working 

 of it much less of a labour, than if rowed in the ordinary way. 

 Were these spiral oars appended to larger vessels, which might 

 be done in such a way as to admit of their being shipped or 

 unshipped at pleasure, they might be of the utmost importance 

 in calms ; and above all, in assisting vessels in distress to work 

 off from a lee shore. 



Their application to the steam-boat, and their superiority as 

 to unretarded power over the wheels at present in use, hardly 

 requires any comment. 



It appears to me that it is not impossible that a machine of this 

 kind might even be applied with advantage as a water-wheel ; and 

 that where a fall of sufficient height for a vertical bucket or cog- 

 wheel could not be commanded, that this spiral wheel might give 

 motion to a corn mill, or any other combination of machinery. 



There is yet another purpose for which it may one day be 

 employed, but for which it would, of course, require to be con- 

 structed ofmuchlighter materials, I mean that of aerial navigation. 

 This art has been hitherto much neglected, chiefly in conse- 

 quence of the ignorant and illiberal ridicule so indiscriminately 

 thrown on those whose genius has led them to occupy them- 



