Polytechnic Association. 923 



Of Boilers. 



Heat, as a motor, is unrivaled, because with proper fuel it may be 

 generated at any time and in any place. The two best mediums for 

 its use are the cheapest and most universally distributed, namely, 

 Water and Air. Of the two, water has the greatest specific heat, yet it 

 is by far the most convenient, since just in proportion to the quantity 

 of water evaporated ■ in a closed vessel the pressure of steam will be 

 increased ; therefore the boiler has become the most generally used 

 generator and receptacle of force. It consists of two parts having 

 entirely distinct functions, namely, the fire-box or furnace, and the 

 metallic shell containing the water and steam. That portion of the shell, 

 including the tubes connected therewith, which separates the water 

 from the burning fuel, and the gaseous products of combustion, acts 

 at the same time as the sole medium through which the heat is trans- 

 ferred from the fuel to the water. 



The application of heat to one side of a metallic plate, and its 

 absorption in sufficient quantity by the water on the other side, result 

 in the generation of steam. The displacement of water from the heat- 

 ing surface in the state of vapor, and its replacement, is the ever- 

 repeated action in the process of boiling. It is apparent that the 

 steam cannot pass away from the heated plate without carrying with 

 it a portion of the water, which should be followed by an equal amount 

 of cooler water, thus forming a current. When this movement does 

 not take place, the whole mass of water is sometimes lifted above the 

 heating surface, and is, doubtless, often the incipient cause of disaster. 

 In vertical tubes, through which the smoke and gases resulting from 

 combustion pass off, the contact of water is impeded by the constantly 

 ascending vapor, and this contest of particles is so great that only the 

 lower portion of each tube is fully effective. To remedy this evil, I 

 propose to fasten on each tube a series of metallic disks or plates, in 

 close proximity to each other, and in an inclined position. When a 

 cast-iron tube is used, these disks are cast on the tube. In a cylindrical 

 boiler, standing on its end, with a fire-box beneath, the vertical tubes, 

 through which the products of combustion escape, are arranged in a 

 circle a few inches from the shell, which, in this case, is not exposed 

 to fire. The disks surrounding the tubes are inclined, so as to be 

 lowest on the side nearest the shell ; they project from one to two inches 

 beyond each tube, and the disks of adjoining tubes are in close prox- 

 imity, or actually united so as to form complete rings, thus the 

 water can only escape by following the direction of the disks, 

 and rising to the inner portion of the boiler. The object of this 



