6l2 



A UTOMA TIC GREENHOUSES. 



pansion box, open on top. This gave 38 feet of 

 two-inch pipe, but experience showed that the boiler 

 was able to heat 80 feet without difficulty. The 

 pipe used was sufficient for the mild weather of 

 last winter, but more pipe would be far better. 

 The boiler was placed on top of a sheet-metal 

 box 14 inches 



(3 



square, and hav- 

 ing a door in front. 

 An opening in the 

 top of the box, a 

 little larger, was 

 covered with an 

 iron grate, and on 

 this the boiler was supported. 

 When in place and connected 

 with the pipes, a round sheet- 

 metal casing was placed over 

 the boiler, resting on the top of 

 the box. This casing had a 

 tight-fitting cover at the top, 

 and in this cover was a two-inch 

 opening, and from this a tin pipe 

 extended under the sash to the 

 back of the house and then out 

 through the post, a cap on top 

 serving to keep out the rain. 



Section of Boiler. 



Figure 5 shows the position of the boiler within the 

 casing. 



It will be observed that all the heat of the gas or 

 oil flames must pass up through the flues of the 

 boiler or along the outside. At the same time all 

 the products of combustion are completely removed 

 and escaped into the open air through the chimney. 

 The boiler and casing were placed directly in the 

 greenhouse under the sash at the south-east corner. 

 The point aimed at was to keep within the building 

 all the heat of the flame. Not only did the water 

 extract a large part of the heat and carry it to all 

 parts of the house, but the box containing the stove, 

 the casing and chimney gave out heat of radiation 

 directly into the house. This explains why a single 

 gas-burner (equal to a common small lamp) kept the 

 house warm. All or nearly all the heat was saved. 

 With both wicks burning in the oil stove the top of 

 the chimney was barely warm, and the hand could 

 be put over the top of the chimney without incon- 

 venience. 



The point is just here — complete utilization of 

 nearly all the heat (perhaps 95 per cent.) directly 

 in the building, a perfectly air-tight building, and 

 a continuous and unvarying source of heat. It took 

 from two to three hours to heat the water pipes, 

 but once heated, the oil stove kept the building 



warm through the coldest nights. No coal or wood 

 fire is ever alike for more than a few moments. A 

 gas flame or oil flame does not vary in intensity 

 after the first ten minutes. Once filled with oil, 

 the stove burned without attention day and night 

 till the oil was exhausted. With a large tank such 

 a stove would heat a greenhouse without attention 

 for several days. With gas there was, of course, 

 no attention needed after the flame was lighted. 



To make the heating apparatus automatic, a valve 

 was placed on the gas-pipe, and this valve was con- 

 trolled through rods and bell-cranks by a thermostat 

 hung on the wall of the greenhouse. The morning 

 sun shining on the glass warmed the building, and 

 under the influence of the heat the thermostat ex- 

 panded and shut off the gas, but not completely, 

 because that would involve re-lighting the gas in 

 case clouds obscured the sun. The flame was 

 merely turned down low. If cloads appeared, and 

 also when the sun began to go down, the tempera- 

 ture fell, and the thermostat contracted, turning on 

 the gas again. The two thermostats worked to- 

 gether, one a little in advance of the other, and 

 sometimes only one operating, as they were set for 

 different temperatures. 



=t7 



Section of Casing, Boiler and Chimney. 



From the experience gained, it is clear that green- 

 houses can be made by these simple means per- 

 fectly automatic. Gas is the best fuel, because it is 

 most easily controlled and practically unlimited 

 m supply. An oil stove requires a large tank to 



