sS79-] BOILERS AND PIPES. 317 



without professing to be an expert in such matters, my opinion is that 

 the apparatus which presents the greatest amount of surface to the 

 direct or first action of the fire, and which can be entirely enveloped 

 in the flame of the furnace, must be the best ; and it seems to me 

 that the boiler which does this is one of the shape of a penny-piece, 

 with a perfectly flat under surface and a slightly convex top, at the 

 apex of which the flow-pipe would start and the returns would enter 

 opposite each other at each side of the penny, — the water-way to be 

 about the usual capacity of the saddle - boiler — that is, from 2 to 

 3 inches thick. I propose to set such a boiler above a shallow 

 circular basin of fire-brick — the fireplace being represented by the 

 bottom of the basin — and to cover it above with another inverted 

 basin of fire-brick brought down to within 2 or 3 inches of the 

 surface of the boiler, the flue going out at the flow-pipe at the crown 

 of the boiler. The boiler would, of course, only be slung by flanges, 

 so as to leave a space about two inches wide round the edges for the 

 draught : the fire being exactly under the centre of the boiler, the 

 draught would be equal all round, and the flame would envelop the 

 whole apparatus perfectly. In order to make the door air-tight, I 

 propose to face it with fire-brick, and work it by a pulley and bal- 

 ance-weight — the door, when closed, dropping on to a bevelled seat 

 in front of the grate, the door itself being bevelled in order to fit. 

 The object of the bevel is to prevent ashes lying on the grate and 

 keeping the door from shutting close. I may state that I have ex- 

 perimented with such doors and found them to work smoothly, and 

 to need no banging or knocking to make them shut — practices which 

 destroy ninety-nine furnace - doors in a hundred. Of course, the 

 door runs in a perpendicular groove in which no obstruction could 

 possibly settle. It may be stated that the furnace-door would be 

 the only brick in the basin below the boiler ; but the fuel is meant to 

 lie on a circular grate of small diameter in the centre of the basin, and 

 when the fire gets fairly ignited the red-hot cinders would be spread 

 outwards round and up the sides of the basin, and the fresh fuel thrown 

 in the centre, thus so far burning the smoke as it passes over the red- 

 hot fuel towards the edges of the boiler. I do not know that I could 

 better explain my ideas without a plan ; but your readers may guess 

 pretty near what I mean by imagining a penny-piece placed horizon- 

 tally in the air, with a saucer of the same size, and a hole in the 

 centre of it, inverted above it, the fire being represented by a candle 

 held under the penny, and the flame travelling over its under sur- 

 face, round the edges, and over the. top and out at the hole at the 

 crown of the saucer. 



And now I will endeavour to record some experiments with a minia- 



