Jaunaij 29, 1874. ] 



JOUBNAL OP HOBTICDLTUBE AND COTTAGE GAEDENEE. 



93 



HEATING— FUEL.— No. 3. 



1.c=7j\=? AVING in a previous paper treated of the 

 ^AnIII different kinds of fuel which may be em- 

 ployed for heating hothouses, I shall pro- 

 ceed in this to consider the extraction from 

 the fuel of the utmost amount of its heat. 

 To effect this we need a furnace, and wish- 

 ing to convey the heat to the place where 

 it is to be radiated, we need a boiler, and 

 from it pipes to convey the heated water 

 to the structure to be warmed, also pipes to 

 return the water to the boiler. We likewise require a 

 flue to carry-off the smoke and other obnoxious products 

 of combustion. Heating by flues or pipes — viz., by hot 

 air, I do not propose to deal with ; for though familiar 

 with that mode of heating from disastrous experience, 

 I have for some years let all my ideas run in the channel 

 of heating by hot water, and to treat of hot air or flue 

 heating would be to take a retrogi'ade step, which is 

 foreign to my intention. 



Now upon the furnace and the boiler over and around 

 it, and it may be under it, we centre the grounds upon 

 which the economy, efficiency, and heating power of the 

 fuel and boiler are to be determined. The furnace should 

 be of such a kind as to insure the complete combustion 

 of the fuel, and the boiler must impart to the water the 

 utmost amount of heat to be obtained from the fuel. 

 Our subject, therefore, divides itself into three parts — the 

 furnace for the generation of heat, the boiler or agent to 

 extract the heat resulting from the combustion of the 

 fui'l employed, and the circulating or heating medium. 



I shall take these in reverse order, for the very ob- 

 vious reason that gas, exceeding in heating power all 

 other kinds of fuel, first claims attention, and fi'om the 

 great number of conservatories and greenhouses in and 

 near our towns capable of being heated by gas it is, 

 probably, of the greatest importance. I am sanguine 

 enough to think that gas will entirely supersede the dirty, 

 smoky, and extravagant use of coal for all household 

 purposes for which the latter is now employed. Nothing 

 has contributed more to our national prosperity than 

 coal, but notliing has been used in so heedless and waste- 

 ful a manner. The waste of the heating power of coal 

 is no doubt greatest in domestic consumption. Half, and 

 more, of the heat afforded by coal is lost by the open fire- 

 grate and cliimney in our dwellings, and it is there for 

 obvious reasons it should be most economised. Wealth 

 is gained by labour of head and hand, and part, a con- 

 siderable part, is spent in securing for its possessor the 

 comforts and necessaries of life — i.e., cooked provisions, 

 dryness, and warmth. In manufacture the loss is not 

 nearly so great, for the profits are calculated by the 

 greatest manufacturing power from the least possible 

 consumption or expenditure of material. To lose half 

 the producing power of any substance would be to 

 make in the profits of manufacture a proportionate re- 

 duction ; but though he has a knowledge of this the 

 manufacturer is as careless as everybody else about his 

 y'l. 670.— Vol. XXVL, New Seeies. 



house fires. It is worth his attention to get as much out 

 of coal as he can in the laboratory of wealth, but he cares 

 so little for it at home as to allow half the heat of the 

 coal to be driven up the chimney. Some hints will be 

 given as to economising heat, not only in warming horti- 

 cultural structures, but in dwellings as well, when I come 

 to treat of boUers heated by coal. 



As regards the circulatory or heating medium, water 

 in a boUer being acted upon by heat is ddated, it is made 

 lighter, and the heated particles ascend, whilst the cold 

 descend by reason of their greater specific gravity : hence 

 circulation is produced, and the water in the descending 

 pipe is heavier, because colder, than that which is in the 

 boiler, and therefore displaces the warmer and lighter 

 water. This cu-culation once established forces all the 

 water in the apparatus to pass successively through the 

 boiler by which it is primarily heated. The action and 

 reaction given the water in the boiler proceeds until aU. 

 the particles are uniformly heated, the water becoming 

 stationary as the heat is exhausted. A properly-con- 

 structed apparatus with a fire at the lowest point keeps 

 the water in continual motion ; as the hot water passes 

 out at the top of the boiler cold comes in at the bottom 

 to supply its place. It is, therefore, necessary that aU 

 boilers should have a free passage for the heated water 

 to flow out at, and an equally free passage for the cold 

 water to enter at the lowest point. It is not only impor- 

 tant that there should be a passage for the hot water out 

 and the cold water into the boiler, but that the passage 

 should be free throughout the pipes or oii-oulatory medium 

 and that must not sufier disconnection, as would be the 

 case were air to lodge and cause a stoppage of the circu- 

 lation. There should not, therefore, be any air remain- 

 ing in the apparatus after it is filled with water, otherwise 

 there wiU be obstruction to a greater or less extent accord- 

 ing to the amount of air. To let out the air, pipes must be 

 inserted at the highest parts of the apparatus, for the air 

 will become fixed if not liberated by an air pipe, and the 

 circulation impeded. The air pipes must be taken up above 

 the highest level of any of the circulatory pipes, and for 

 the due expansion of the water from heating should not 

 be less than 9 feet in length or perpendicular height above 

 the highest point of the apparatus. If of less height the 

 water is forced out of the mouths or ends of the pipes. 

 A small metal three-quarter-inch gas pipe galvanised, or 

 lead half-inch, strong or heavy, as the lighter descriptions 

 soon wear out, answers very well, the end of the pipes 

 being bent downwards to prevent anything getting in and 

 closing them. These au- pipes ought not to be taken out- 

 side or communicate by their ends with the external air, 

 as I have known the water freeze in them ; therefore for 

 any good they are they might as well be dispensed with ; 

 but we must, nevertheless, have the air out of the pipes, 

 and allow space sufficient above the other parts of the 

 apparatus to hold the water on its expansion, and hence 

 I do not advocate air pipes with taps, though there is no 

 objection to them when the circulating medium is em- 

 ployed in heating different compartments on varied levels. 

 These short air pipes with taps ought to be employed at 



No. 1S22.— Vol. LI., 0;.o SEams. 



