March 20, 1873. ] 



JOUENAL OF HOBTICULTUBE AND COTTAGE GARDENEE. 



237 



HEATING— FUEL,— No. 1. 



WING to the present high price of coals it is 

 probable that many persons ■will be pre- 

 vented from indulging in forced flowers, 

 fi'uits, and vegetables to the extent they 

 have been accustomed ; ■whilst as all ma- 

 terials of construction are greatly enhanced 

 in cost, serious ob.stacles ■wiU be placed in 

 the path of those contemplating the erection 

 of horticultural structures. The prices of 

 bricks, stone, mortar, glass, and -wood are 

 Mgher, but then- cost has advanced far less in proportion 

 than that of labour, ■which, except in the case of the 

 -gardener, has been variously increased by 10, 20, or '25 

 per cent. Iron has attained such a price as to cause those 

 favouring it for the construction of horticultural erections 

 to think twice before they give an order, and the cost of 

 iron pipes for heating by hot ■water must, I am afraid, 

 ■deter many from adopting them as a mode of heating. 



Apart from the first cost of providing for heating a 

 house or range of houses by hot ■water, as compared with 

 that of heating by hot air, the increased price of fuel 

 leads to the consideration not of which is the best mode 

 ■of heating, but which, affording under judicious manage- 

 ment satisfactory results, is the most economical. The 

 cost of heating by hot water has not, so far as I am 

 aware, been considered from an economical point of 

 ■view, its superiority in this respect having been estabhshed 

 over heating by hot air or flues. The apparent difference 

 as regards the effects on vegetation between heat radiated 

 from brick, stone, or the hke, and that from hot-water 

 pipes, results not so much from the radiating material as 

 from the mode of applying the heat. The difference 

 between a hot-water pipe and a flue is just this — by 

 the former the heat is given off, or the air of the house 

 warmed, by pipes uniform in temperatm-e, or very nearly 

 60, througliout their extent ; whilst by the flue the heat 

 is radiated at a temperatm-e considerably higher where 

 the flue enters than it is after the flue has passed along 

 half the length of the house, to say nothing of its exit. 

 Another evU of heating by hot au' is that the products of 

 combustion are carried along with the heated air, and 

 find their way through the cracks of the materials, and, 

 as everybody knows, are not beneficial to vegetation ; but 

 there is no such objection to heating by hot water. It 

 cannot be said of hot aii- that it is so desirable for heating 

 greenhouses and hothouses as hot water — in fact, my 

 experience of flues prompts no word in their favour. 



I should be unwilling to say that hot air is more econo- 

 mical than hot water were that proven, and to my mind 

 it is not. It is more costly to have a boiler, iron pipes, 

 &c., for heating by hot water than to have a furnace and 

 flue for heating by hot air. The first cost is gi-eater — 

 double or treble, but there is no sa^ving of fuel. In heating 

 by a flue the brickwork of the furnace absorbs and retains 

 a gi-eat amount of heat. This is radiated fi'om the ex- 

 terior of the furnace setting, and is lost to the house ; 

 only when the heat of the fire is less than the heat of the 

 Ma. 62S.-VOU XXIV., New Series. 



furnace surroundings can the house derive any benefit 

 from the heat absorbed at tlie furnace. This being the 

 case with a furnace for affording heat to a house, it may 

 be singular that a corresponding waste of heat does not 

 result in the case of a furnace for heating by hot water. 



As regards the majority of furnaces for boiler heating, 

 there is not much more to be said in their favour than in 

 that of the furnaces constructed for heating by flues. 

 The sides of the furnace are brickwork, and are heated 

 to a temperature of 1141" (the heat of a common fire, 

 according to Daniell), while the heat on the fuel over a 

 fire of this kind (the fuel not burned through) is not suffi- 

 cient to melt lead (59-4°). Thus we have in the furnace a 

 heat that would melt lead, zinc (700-), antimony (810'), 

 and we only act on the boiler ■with a temperature of little 

 more than haK that of the bricks. In this case we lose 

 half the heat of the fire when the fuel is not burned ; but 

 when the whole of the fuel is brought to a red heat we 

 act directly on the boiler with a temperature of consider- 

 ably over 1000% and yet we lose the heat at the sides of 

 the furnace ; and the end of the furnace opposite the door 

 being of brick that is made red hot. The heat may then 

 pass through the boiler, surrounded by water, and not 

 unfrequently it passes along the sides, heating quite as 

 much brickwork as iron of holding water. In some cases, 

 too, it passes over the top of the boiler heating the top of 

 the flue very much more — though there we do not want 

 the heat — than the bottom, where we have water which 

 we wish to be heated. We expend in fact one-half, and 

 in some cases more than half, tlie heat of the fuel in the 

 furnace without deriving any corresponding benefit. 



In my opinion the heating powers of a boiler or boilers 

 are wholly dependant on the surface the boilers expose to 

 the action of the fire ; direct, the exposure is the most 

 important, but the indirect is not insignificant. What 

 must be the waste of fuel when half of its heat is expended 

 on surrounding surfaces, and half of that heat passing 

 over the sm-face of the boiler escaping by the chimney ? 

 I know that some contend, or have done, that the side 

 heat of a furnace is of no use for heating a boiler, that 

 hollow grate bars are an evil. Professing no knowledge 

 of the theory of heat beyond what has been verified by 

 my own experience, I confess to being at a loss to explain 

 why any material in contact, whether below or at the 

 side of a red-hot fm'nace fire should not be heated. I 

 know that the sides of a boiler furnace are made red hot, 

 and the grate bars are burned through. No better illus- 

 tration can be given of the value of the side heat of a 

 furnace for heating than having a boiler fixed behind and 

 at the side of an ordinai^y house fire. With properly 

 fixed hot-water pipes it will heat a room equal in extent 

 to that in which the fire is situated. Thus we secure 

 double the heat from the same fuel. There is no loss of 

 heat to the room, but a clear saving of heat cent, per 

 cent. 



Again, let us have a boiler fixed on the fire ; it shall be 

 so set that the fire can act on its lower and front surface, 

 but not on the back, the heat being made to pass in 

 front to the chimney, and from this again we get hot 



No. 1177.— Vol. XLIX., Old SERiaa. 



