HEATING BY HOT- WATER PIPES. 



187 



such circumstances very rapidly, five or 

 six times as much fuel as is really neces- 

 sary will be consumed by a gardener 

 zealous of the honour of his apparatus. 

 It is of course possible, by having a fur- 

 nace and boiler excessively large in pro- 

 portion to the pipes, to construct an 

 apparatus with 4-inch pipes which shall 

 boil in an hour ; but the necessary con- 

 sequences will be, that such a furnace 

 would burn, during every hour of the 

 night, four times as much fuel as can 

 possibly be effective in heating the build- 

 ing to which it is applied. 



" If a house is to be heated rapidly, the 

 pipes should be of the smallest diameter 

 which is "consistent with a free circula- 

 tion ; but it must be borne in mind that 

 such pipes will also cool with equal rapi- 

 dity ; — and if the heat is to be main- 

 tained through the night, the furnace 

 must be so constructed as to contain a 

 large quantity of fuel, but only to allow 

 of a very slow consumption. Now such 

 a furnace, though theoretically very easy, 

 and practically not very difficult of con- 

 struction, requires an almost scientific 

 nicety of management not to be expected 

 from common gardeners. There are, 

 moreover, several objections to small 

 pipes, one of the most material of which 

 is this — that, the motion of water within 

 them being retarded by friction, in a 

 much larger degree than in large pipes, 

 they can never be brought to so high a 

 mean temperature. So that under simi- 

 lar circumstances of pressure, &c, 200 

 feet of 1 - inch pipe could never be 

 made to produce the same effect as 50 

 feet of 4-inch pipe, though their surfaces 

 would be nearly equal. 



" A little consideration will enable us 

 to determine, whether such rapid com- 

 munication of heat be really essential 

 to the efficiency of a heating-apparatus. 

 In hothouses, where permanent heat is 

 required, it is evidently unnecessary. 

 The only place where it may be desired 

 is in buildings where occasional heat only 

 is required. The real desideratum is, a 

 furnace so constructed that it shall con- 

 tain fuel enough to supply the pipes with 

 as much heat as they can radiate during 

 the night, and which may be depended 

 upon for burning steadily and perfectly 

 whatever fuel is put into it — not with 

 that accurate precision requisite where 



the temperature of the house depends 

 upon the exact amount of combustion 

 per hour, but sufficiently slow to allow 

 the water to absorb the greatest possible 

 portion of the heat generated. With 

 such an apparatus, the fire being once 

 effectually lighted, the gardener need be 

 under no apprehension that the heat 

 during the night will prove insufficient, 

 though it may be several hours before 

 the pipes attain their maximum tempera- 

 ture. 



" I have dwelt somewhat at large on 

 this point, because it is one on which 

 much mistake exists, and under this mis- 

 apprehension the best apparatus may be 

 condemned as defective, and a very im- 

 perfect one preferred and adopted in its 

 stead ; — that which is commonly adopted 

 as a criterion of excellence being really a 

 proof of defective construction. 



" There can be, on the whole, no 

 doubt that 3-inch or 4-inch pipes are ex- 

 ceedingly preferable to smaller ones, 

 where economy of fuel and uniform ad- 

 justment of the temperature for several 

 hours are the primary objects. Where 

 ornament or great economy of space is 

 important, and economy of fuel is not 

 much considered, smaller pipes may be 

 employed; but where rigid heating is 

 considered essential, I believe it will be 

 found best to have recourse to the old 

 expedient of brick flues; — and their atten- 

 dant inconveniences must be considered 

 as the price paid for this advantage, real 

 or imaginary. 



" The next point to be noticed is the 

 absolute amount of heat produced by any 

 hot-water apparatus, which depends on the 

 proportion between the surface of pipe 

 and the surface of external glass in the 

 building. The laws both of cooling by the 

 glass and of radiation from the pipes have 

 been so ably and so accurately treated 

 by Mr Hood," in his excellent treatise so 

 often quoted in this work, " that there is 

 nothing to desire on this head. Almost 

 all the earlier apparatuses are incompe- 

 tent to the work required of them, the 

 quantity of pipe being utterly insufficient 

 to produce the heat required ; while, the 

 boiler being large, and of very defective 

 construction, a vast quantity of fuel was 

 burned to waste. The gardener, finding 

 his heat deficient, naturally stokes up the 

 fire and throws on fuel, in the hope of 



