486 TRANSACTION* OF THE 



feet long and one and a half inclies diameter, set five-sixteenths apart. The 

 waist is so constructed as to cover within one-fourth inch of the tubes. 

 These boilers are said to work well ; but I doubt whether they work so well 

 as boilers with more room for the circulation of water. 



There have been upright tubular boilers in which the flues did not pass' 

 through the steam room, but were covered with water; and a smoke-box, 

 fiomewhat like the fire-box, occupied the middle of the steam space. This 

 arrangement is to prevent the burning of the tubes ; but it substitutes the 

 burning of the smoke-box, which is dangerous — if there ia burning at all — ■ 

 and it diminishes the steam room and water-level, and makes the boiler 

 complex and expensive, and difficult to repair. And all this trouble is 

 incurred for the sake of avoiding an evil which, so far as I can learn, does 

 not exist in fact. If any one present can testify as to its existence, I 

 hope he will do so; but I hope no one will tell us what he imagines, or has 

 got from the imaginations of others. 



On the whole, I consider the simplest form of the upright tubular boiler 

 88 the best. It is the cheapest, has the fewest joints, is easiest to repair, 

 dries the steam, and is durable if kept clean. 



There is another type of boiler in which the water is inside the tubes, 

 for marine use, when the boiler is so large that men can go inside to clean 

 and repair the tubes, it does well; but for small boilers, in which the joints 

 are not accessible without taking off top or bottom plates, it is not good in 

 any case ; and it is never good unless the smoke-eurrent is at right angles 

 with the tubes. If it be parallel with the tubes, the heat is not communi- 

 cated so well as when it passes through small flues. In Montgomery's 

 boiler, the smoke passes swiftly across the upper ends of the tubes, and then 

 decends, and returns under a diaphragm. In Morton's boiler, the tubes 

 are shorter than in Montgomery's, and there is no return of the smoke. 

 Both agree in giving a rapid movement to the smoke, which insures its 

 impinging against the tubes, so that each particle shall have a chance to 

 come into contact. But when smoke goes through straight and smooth 

 passages that are large, the middle of the current does not impart its heat. 



There is a composite boiler^ made up of water-tubes with flues through 

 them. The first of this kind was patented by Ogle & Summers, in 1830 

 or '31. It had chambers at top and bottom, so that the water circulated, 

 descending through an outside pipe, and ascending in the annular spaces 

 between the water-tubes and their internal flues. The smoke ascended 

 partly through the flues, and partly between the tubes. This boiler vapor- 

 ized 4 1-5 lbs. of water per foot of surface — one sixth as much as the old 

 locomotives ; and it required to be worked under a pressure of 247 lbs. to 

 give it its best effect. The water-tubes were 4 inches, and the flues 1^ 

 itiehes, leaving about 1^ water-spaces. The fan-blast was used, being found 

 more effective than the steam-jet ; and the consumption of fuel was about 

 1 lb. for 5^ lbs. of water. 



Messrs. Lee & Larned use the annular arrangement in their steam fire 

 engines ; but they have a steam drum much larger than the chambers of 



