Polytechnic Association Proceedings. 721 



sixty-horse power by adding tubes at the top, raising up the steam 

 di'um and its connections, and buildinsr the side walls higher, but 

 without disturbing the foundations or walls already erected; or 

 it can be enlarged to any extent by taking down one or both side 

 walls and adding tubes at the side, and top also, if desired. This 

 is certainly a valuable feature. 



If, for instance, a forty-horse power boiler of any of the ordi- 

 nary forms is not large enough, it must be sold at a sacrifice, a 

 larger one put in its place, at the full price, and the serious expense 

 and loss of time from changing must be incurred. Or, on the 

 other hand, a large safety boiler may be divided into smaller ones. 



For a steady demand upon the boiler, as in driving an engine, it 

 works well without any steam drum. Where large amounts of 

 steam are required at irregular intervals, we have put on drums 

 running across the boilers, of eighteen and twenty-four inches 

 diameter. The longitudinal drums, running the whole length of 

 the tubes on the same inclination, are preferred by some, as thej 

 give additional water and steam room, and are made twelve and 

 eighteen inches in diameter, and oi ample thickness, thus giving 

 them great strength and safety. 



There are no new conditions in tliis boiler, as putting the water 

 and steam inside of instead of around the tubes, is not new, and has 

 been in successful use for many years. 



Its ])rincipal novelty, and which we claim as a valuable one, is 

 the perfect simplicity of the mode of connecting the tubes together, 

 and the uniformity in size and shape of its parts. 



To sum up, we have thrown aside the dangerous portion of ordi- 

 nary forms of boilers, the shell, which is also the uneconomical and 

 destructible part, and have composed our boiler entirely of the 

 safe, economical and durable portion, the tubes. 



DESCRIPTION. 



The anncxxed illustrations represent tliis boiler with the walls 

 cut away, so as to show the internal arrangement. The boiler is 

 composed of wrought iron tubes, -4, A. 



Upon both ends of each tube are firmly screwed the cast iron 

 heads, jB, B, which form the front and rear ends of the boiler 

 when laid up. These joints are necessarily tight, being screwed 

 on in a lathe. 



The tubes can be laid up in vertical rows, or each horizontal row 

 may be pushed three inches or one-half the width of the square- 



[Inst.] 46 



