GLASS STRUCTURES AND APPLIANCES. 



281 



a circulation of air. All stoke-holes, it is needless 

 to say, should be XDrovided with a deep drain, and 

 protection from the elements. 



Fuel. — The cost of fuel varies so much in 

 different parts of the country as to render it im- 

 possible to say what will be found most economical 

 in any particular district. This fact does not, how- 

 ever, prevent us from saying what experience has 



be well set, pipes in plenty properly fixed, the whole 

 apparatus in first - rate working order, and yet 

 success or failure will depend upon the attention 

 and ability of the stoker. If a skilful hand, he will 

 see that his supply cistern is full of soft water, air 

 taps and valves in working order, stoke-holes and 

 ash-pits clean and free from refuse, waste, and 

 clinkers. If coal is used it should be placed on the 

 dead-plate to coke before it is passed on to the fire. 



I I I I I r 



Front 



proved to be the best. 

 Some furnaces, nota- 

 bly the saddle, will 

 burn any kind of fuel. 

 Bituminous coal, an- 

 thracite, coke, and 

 wood when plentiful, 

 may be used for almost 

 any kind of boiler ; 

 but where good coke 

 can be obtained it is 

 undoubtedly the best. 

 Bituminous coal under 

 slow combustion is apt 

 to distil rather than 

 consume, when the 



bars and tubes become choked, and the heat is lost. 

 Anthracite, like coke, gives off no smoke, and on this 

 account is suitable for use near mansions, where 

 smoke would be a nuisance. Moreover, in the com- 

 plete control of draught it forms an excellent slow 

 combustion fuel for large boilers ; but it is not so 

 well adapted to small ones. The worst fuel is coal 

 which contains sulphur, for if present to any great 

 extent, its effect on the plates and rivets is very 

 rapid and destructive. 



Stoking. — Although stoking has been left till 

 last, it is by no means the least important item in 

 economical hot-house management. A boiler may 



Ground Plan Chir 



Fig. 69.— Mode of Setting Plain Saddle Boiler, 



Back 



Too much should not 

 be introduced at one 

 time, when the draught 

 regulated by the dam- 

 per will increase or 

 check the escape of 

 heated gasas into the 

 chimney. A careful 

 stoker will keep his 

 fire-doors closed, other- 

 wise a large quantity 

 of cold air will pass 

 between the fuel and 

 the bottom of the 

 boiler, which it will 

 cool to a considerable 

 extent. Fresh air is, however, necessary to combus- 

 tion, but it should pass through the bars of the grate, 

 when the heated gaseous matter will rise upwards to 

 the bottom of the boiler, where, if the outlet is neither 

 too large nor too high, a greater effect will be pro- 

 duced than if too easy an outlet is allowed into the 

 chimney. When the fire is burning clear and heats 

 are up, a furnace can often be shut up quite close 

 for hours together, when a draught would mean a 

 loss of fuel and possible injury from o"verheating. 

 As a rule constant feeding tends to waste of 

 fuel, and the introduction of too thick a layer 

 necessitates the admission of too much air above 

 as well as below the fire-bars, while too littlft 



