PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 563 



of the fire; to increase, therefore, this surface, is the aim and object 

 of most improvements in steam boilers. There is, however, 

 another fact not so universally known, which, however, is daily 

 more acknowledged, viz : That one square foot of heating surface 

 at, over and around the fire is worth more than ten square feet 

 tw^enty or thirty feet from the fire. The constantly increased 

 dimensions of the locomotive fire box is the best practical illustra- 

 tion. It is also well understood that the thinner the sheet of water 

 exposed to the action of the heat the more rapid will be the pro- 

 duction of steam. The object of this invention is, therefore, to 

 construct a fire box presenting the largest possible amount of sur- 

 face to the direct action of the fire, and keeping in contact with it 

 only a thin film of w^ater, in such a manner that no matter how 

 rapid the evaporation may be, the same thickness of water be 

 always in contact with the surface exposed to the fire. These 

 steam fire boxes add fully one hundred square feet of heating sur- 

 face to any steam boiler. When we now find that a forty-eight 

 inch diameter boiler, with two flues, eighteen inches diameter, each 

 thirty-six feet long, contains three hundred and ninety-six square 

 feet of heating surface, and remember the fact that the surface of 

 the first ten feet over the fire, containing eighty square feet, is the 

 most valuable portion of the whole boiler, it must be apparent to 

 any practical mind that the addition of one hundred square feet of 

 surface on each side of the fire, and in immediate contact with the 

 same, will double the steam capacity of the boiler, to say nothing 

 of the important fact that the sheet of water exposed to the fire 

 in these boxes is one inch in thickness, whereas the body of water 

 in the boiler, exposed to the action of the fire, has an average 

 thickness of twenty-four inches. 



The principle feature of the improvement consists in a series of 

 vertical tubes or cells, arranged upon each side of the boiler, and 

 forming the side walls of the furnace. Fig. 1 represents it as 

 applied to the common cylindrical boiler ; the brick work being 

 removed so as to show the plan more full}^ The series of vertical 

 pipes A are arranged upon each side of the boiler, in close proxi- 

 mity, and have open communication with each other at their upper 

 and lower ends. This series of pipes are fastened to each other 

 by bolts passing through the flanges at the transverse openings at 

 the ends, and are also more securely fastened by iron rods that 

 pass horizontally through the upper and lower chambers — the 

 ends of these rods passing through the covers or caps of the cham- 



