PROCEEDINaS OF THE POLYTECHNIC ASSOCIATION. 501 



The hour for adjournment having arrived, no opportunity vv^as given to 

 hear objections to the foregoing plan. 



The subject of " Plate Armor" was therefore continued for the next meetr 

 ing. Adjourned to November 12th. 



American Institute Polvtechnic Association, ) 

 November 12th, 1863. j 

 Chairman, S. D. Tillman, Esq.; Secretary, Mr. B. Garvey. 



New Submerged Paddle Wheel. 



A model of a new propeller, by Mr. Leer, of Boston, was exhibited and 

 examined. 



The Chairman. — The principle involved in this model appears to be that 

 as the wheel turns it tends to throw the water out from it by centrifugal 

 force, aided by atmospheric pressixre. A hollow is made in the shaft to 

 let the air in and thus press the water out of the center. There are two 

 wheels, one each side, and placed a little above the stern, and worked 

 horizontally, which adapts them to boats of light draft. Mr. Leer claims 

 that this method is superior to the side wheel and the ordinary propeller. 

 But the only novelty I can see in it is in having the hollow in the shaft, 

 without which there would be a pressure of fifteen pounds on the square 

 inch, which the wheel would have to work against. The other parts of 

 this wlieel are not new. They are embraced in that known as the " Hunter 

 wheel," which I believe is now abandoned. There is a loss of power with 

 every paddle wheel and screw propeller. But in the Hunter wheel, which 

 is virtually a paddle wheel partly enclosed in a case, the loss of power is 

 great, because a portion of the water is carried entirely around the wheel 

 and against the inside of the case. Ericson's " Iron Witch," a North river 

 steamer, tried about fifteen years ago, had two small partially submerged 

 paddle wheels. It was a failure. 



Mr. G. Bartlett. — The Hunter wheel is well known by Mr. Leer, and he 

 claims that his plan remedies the defects in it. 



New Furnace for Boilers. 



Mr. Manton exhibited a model of his furnace for utilizing the waste heat 

 which passes up the chimney of steam boilers. 



Mr. J. K. Fisher. — The operation of this invention consists in causing the 

 heat and smoke, after it has passed through the furnace, instead of being 

 thrown out into the air, to circulate through a mass of fire bricks and pieces 

 of scrap iron, or any other material capable of absorbing heat. By this 

 means the mass is heated to some 1,300 degrees, when a damper shuts off 

 the heat from passing through this material, and turns it into a similar mass 

 adjoining. The air which feeds the furnace is now made to 'pass through 

 this heated mass of scrap iron and broken fire bricks, which supplies the 

 fuel with hot air, and thereby effecting considerable economy. As has been 

 stated, there are two of these air heaters, which are used alternately, so 

 that when one is feeding the fire with hot air the other is absorbing the 

 heat, which would otherwise pass up the chimney. In ordinary practice 



