SECTION XI 

 Heating Apparatus 



Market growers and nurserymen who have to erect large greenhouses 

 for their crops do so strictly on business principles. The ornamental 

 structures seen in private gardens and public establishments do not appeal 

 in the least to men who have to grow plants for a living, and who erect 

 glass structures not because they like to, but because they must. Not only 

 must money bo spent in the erection of glasshouses and frames, but a 

 suitable temperature must be maintained in them by means of artificial 

 heating. In the old days, before hot -water pipes came into use, glass- 

 houses were heated by means of "flues", and in very old gardens some 

 of these still exist. Flues consist of a passage from the furnace up and 

 down one side, or all round, a house, and enclosed by tiles or bricks in 

 such a way that sulphurous fumes shall not leak into the house and 

 destroy the plants. The heat and smoke are carried along these flues, and 

 find an exit in the chimney. The heat obtained from the flue surfaces was 

 much or little according to the way the furnaces were fired, and excellent 

 results were obtainable by this method of heating. 



The flue system, however, is now obsolete, and no one would dream 

 of heating a modern glass structure by it. Hot- water pipes and boilers 

 have come to stay, and taking everything into consideration, they not only 

 supply all the heat required, but they can be regulated by means of valves 

 to raise or lower the temperature. Not only that, but hot-water pipes can 

 be arranged wherever the grower wishes either along the floor, around 

 the walls, under or over the stages or benches, and along the roof itself 

 if necessary. Indeed in many modern glasshouses in large market nur- 

 series 4- in. pipes are run along the entire length of a house overhead. 

 It is claimed for this method of heating that the air throughout the house 

 is kept at an equable temperature, and in the event of severe frosts no 

 danger is to be apprehended to plants inside near the glass. The installa- 

 tion of these pipes overhead naturally entails extra expense, but that is 

 counterbalanced by the great advantages derived. The pipes are supported 

 at intervals by Uprights, so that there is no strain upon the roof or sash 

 bars. Although 4-in. pipes are generally used, 3-in. and 2-in. are also- 

 employed under special circumstances. 



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