402 TRANSACTIONS OF THE 



about a horizontal axle passing longitudinally through the ship, and put in 

 motion by a steam engine ; and it was found on experiment to work well, 

 and to have a propelling power equal to the paddle wheel. 



This screw has undergone various modifications. In one improvement 

 the helix is made of two parts, each equal to half a revolution, placed at 

 a small distance from each other on the same axle. By this disposition it 

 is supposed that the escape of the water, after it has been acted upon by 

 the screw to propel the vessel, will be facilitated, and, I may add, all the 

 disadvantages of back water overcome by perforations in the arms near 

 the " hub," as recently patented in England. 



In regard to the navigation of our canals by steam, the washing of the 

 banks seems to be one of the great points to be accomplislied. I do not 

 hesitate to say that it cannot be entirely avoided. It is impossible to move 

 any body, be it ever so small, in water witliout displacing it to some ex- 

 tent. Drop a piece of stone in a glass of water, you displace it in every 

 part just in proportion to the bulk of the stone. So a vessel passing dis- 

 places the water on either side in proportion to its bulk in the water. This 

 causes a rise and fall or undulated wave on the shore — not so much at- 

 tributable to the motion caused by its propelling power, as to the displace- 

 ment following the passage of the cut-water through the water. Various 

 modes might be proposed to got rid of the motion caused by the wheels or 

 propellers, could we get rid of the displacement. Setting the wheels at such 

 an angle as to throw the motion on the center of the canal, or the more 

 recent and scientific plan, as shown on Montgomery's Archmedean propel- 

 ler, being the ordinary screw propeller, with a rim controlling the flow of 

 water in a line parallel, or rather consequentive with the shaft. 



The use of the propeller on the Delaware and liaritan canal, will show 

 that, in order to make steam profitable to canal navigation, the canal must 

 be made suitable first ; and unless the banks of the canal are secured by 

 sheet piling, stone or masonry, all methods to introduce steam will be found 

 more or less objectionable, inasmuch as it will be impossible to acquire any 

 considerable speed without washing the banks just in proportion to such 

 speed ; and the most we can hope for will be a slow speed, but a little be- 

 yond that of horse power. 



Mr. Stetson said that we can learn much from Soule, of Manchester, 

 whose researches are highly valued for scientific and practical character. 

 We find that out of all the power we make, we only realize from five to 

 ten per cent of it in utilizing it. 



Mr. Eeed. — Steam will extinguish incandescent coals, and when applied 

 in the holds of ships or any tight rooms, will reach every particle of fire 

 and put it out — it abstracts all the oxygen, so that fire cannot live in it. 



Mr. Sewall. — Pipes to carry steam from the boiler to the interior of the 

 vessel, were tried in our steam frigate ]\Iississippi. 



Mr. Seeley. — Steam for extinguishing fire was suggested twenty-five 

 years ago. Flame is extinguished by steam — heat remains. Diificult in 

 application to buildings, on account of the access of air. 



