222 



THE GARDENER'S ASSISTANT 





Temperature at which the House is to be kept. 



Tempera- 





ture of 



^ - A s 



External 



45° | 50° | 55° | 60 c | 65° | 70° | 75° | 80° | 85° | 90° 



Air. 



Number of Feet of 4-inch Pipe. 



10' 



126 



150 



174 



200 



229 



259 



292 



328 



367 



409 



20 



91 



112 



135 



160 



187 



216 



247 



281 



318 



358 



30 



54 



75 



97 



120 



145 



173 



202 



234 



269 



307 



32 



47 



m 



89 



112 



137 



164 



193 



225 



259 



296 



40 



18 



37 



58 



80 



104 



129 



157 



187 



220 



255 



50 







19 



40 



62 



86 



112 



140 



171 



204 



Pipes heated to 200° are likely to do harm in 

 a plant-house, and we should recommend half 

 as much piping again as that given in this table. 



Heating by Steam. — This mode of heating is 

 now entirely superseded in this country by that 

 of hot water, which is cheaper, more easily 

 managed, and can readily be applied on a small 

 scale. It is very largely employed in horticul- 

 ture in the United States of America, where, 

 owing to sudden changes in the external tem- 

 perature, it is necessary that the artificial heat 

 should be easily controlled. The steam appa- 

 ratus is so contrived that the pipes can be 

 made quite hot in a few minutes, and as 

 quickly cooled by letting out the steam. Pipes 

 can be heated by steam to a much higher degree 

 than by hot water, unless the latter is kept 

 under pressure, but an intensely heated surface 

 renders the air less favourable to the growth of 

 plants than one which is only heated to 150°, 

 and without exceeding this temperature we can 

 get from an easily-managed apparatus as much 

 heat as is desirable. 



Heating by Gas is a convenient and cleanly 

 mode of preventing injury from frost in small 

 structures, such as greenhouses and conserva- 

 tories attached to suburban residences; and if 

 the products of the combustion of the gas be pre- 

 vented from escaping into the house, the plants 

 growing in it are in no more danger of injury 

 than where any other mode of heating is em- 

 ployed. Various methods of heating by gas 

 have been devised, water being generally the 

 medium of conveying the heat. One of the best 

 is that patented by Mr. G. Shrewsbury, of 

 Lower Norwood, and which is made of various 

 sizes. Fig. 292 shows one adapted for heating 

 a small conservatory, the length of pipe neces- 

 sary being of course regulated by the size of 

 the house. 



The apparatus consists of a cylindrical boiler 

 with flow and return pipes communicating with 

 a pedestal tank. Through the boiler run several 

 tubes, wide below and contracted above, and 

 directly under these tubes are placed the bur- 

 ners, which are constructed on the principle of 



the Bunsen burner, and are screwed into a flat 

 gas-tight box connected with the supply-pipe. 

 The object of the gas-box is to secure an equal 

 supply of gas to all the burners, and the box is 

 made to swing out of the door of the outer case 

 for convenience of lighting. When the gas is 

 once alight the apparatus maintains a steady heat, 

 and requires no attention beyond from time to 

 time putting a small quantity of water into the 

 feed-cistern to supply any loss that may have 

 taken place. Mr. Shrewsbury states that about 

 a pint a week is enough, but much would de- 

 pend on the size of the boiler, the heat at which 

 the water is kept, and other circumstances. If 

 a down-draught can be guarded against, the 

 apparatus may be fixed inside a conservatory 



Fig. 292.— Shrewsbury's Gas-stove. 



without any risk to the plants. No smoke is 

 emitted from the burner, for the products of 

 combustion being a light vapour, are carried off 

 through an escape-pipe from the top of the 

 boiler. But to render these apparatus suitable 

 for all circumstances, they are made so that the 

 pipes can be fixed inside the house, and the 

 boiler on the outside or beneath, as convenience 

 may allow. If the former, the boiler requires a 

 wood casing to protect it from the inclemency 

 of the weather. Modifications of this apparatus 

 have been attached to large oil lamps such as 

 Clarke's Patent Syphon, Rippingille's Patent, 

 &c. One great advantage of using oil- or gas- 

 heated boilers for small greenhouses or conser- 

 vatories is, that those whose other avocations 

 preclude their attending to fires in the day 

 can leave them burning during severe frost. 

 Small greenhouses attached to a dwelling-house 

 can be heated from the boiler attached to a 

 cooking range or kitchener. [J. B.] 



