218 



THE GARDENER'S ASSISTANT. 



heat of the burning fuel strikes against this 

 back before ascending into the centre flue, in 

 passing through which it is diverted into flues 

 right and left, and so on to the top of the boiler, 



Fig. 281.— Gold-medal Boiler (elevation). 



whence the smoke is conducted into the chim- 

 ney-shaft, and by the time this is reached nearly 

 all the heat is absorbed. This boiler is very 

 durable, and is easily set, there being no corn- 



Fig. 28-2.— Gold-medal Boiler (longitudinal seetion). 



plicated flues; and it will consume any kind of 

 fuel. In the figures a shows the ash-pit, b the 

 fire, c the centre flue, d the right and left return 

 flues, e water-way end, / sliding soot-door for 

 cleaning flues, with fire-brick casing, g sludge- 

 plugs for cleaning interior of boiler, h flow-pipe, 

 i return-pipes, I hollow sj)ace around the boiler 

 for utilizing the heat given off by its exterior 

 surface. This is virtually a flued saddle-boiler, 

 of which there are many variations in use. 



The Witley Court, Phoenix, Paragon, Allerton 

 Priory, and Imperial are all improved saddle- 

 boilers constructed mainly on the same principle 

 as the Gold-medal here figured. 



Stevens' Improved Cornish or Trentham Boiler 

 (fig. 283) is another powerful form, not strictly 

 speaking a saddle-boiler, being only a modifica- 

 tion of the well-known Cornish steam-boiler. 

 The great amount of work done by the latter 

 with a small expenditure of fuel is a matter of 



notoriety among engineers, and a proof of the 

 soundness of its principle. 



This boiler consists of two wrought -iron 

 cylinders welded together in a very substantial 

 manner, having about 3 inches of water space 

 between the cylinders, and the door-frame being 

 firmly attached at the end. The boiler is car- 

 ried by two cast-iron chairs, shown at a, a, the 

 front chair forming the frame for the lower 

 flue-doors; these doors, b, b 3 fasten by a simple 

 catch, and can be lifted off for sweeping, clean- 

 ing, &c, with the greatest facility. At the 

 bottom is a plug, c, which should be unscrewed, 

 and all accumulations of dirt thoroughly raked 

 out of the interior, once in three or six months, 

 according to the tendency of the water to 

 deposit solid matter. The furnace doors, one 

 of which is open, are shown at d, while e is the 

 flow-pipe and / the return-pipe. In setting, the 

 chairs are placed on a level foundation, and two 

 solid brick walls built so as to clear the boiler, 

 are carried up to about half the depth of the 

 cylinder; here a course of fire-brick lumps is 

 worked on and brought up close to the side of 

 the cylinder, and resting on these an arch is 

 turned over the top, leaving a narrow space 

 about as deep as the top flue-doors, to serve as 

 an upper flue, while the space below the fire- 

 brick forms a lower flue. The grate bars are 

 inside the cylinder towards the lower part, the 

 space beneath them thus forming the ash-pit, 

 and that above them the furnace. The heat 

 therefore passes through the centre of the 

 boiler first, then returns over its upper half, 

 and finally is conducted under the lower half on 

 its way to the chimney-shaft, which mode of 

 setting is found to give better results than when 

 the heat is first conducted below the boiler. 

 The principle of this boiler is such as not only 



Fig. 283.— Stevens' Improved Cornish Boiler. 



to expose a large area of water space to the 

 direct action of the fire, but the heat operates 

 with its greatest force on the upper part of the 



