206 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 



go out before bed-time, and find the sky clear and frosty, con 

 trary to your anticipations in the early part of the evening, — 

 and how often do we find this really to be the case, — you enter 

 into your green-house, and you find the thermometer travelling 

 down rather quickly towards the freezing-point. Kindling fires 

 is generally an unpleasant business at this time of night, and 

 we are pretty often incnned to let the plants take their chance, 

 rather than be at the trouble of doing it, even if it should cost 

 us half a night's sleep through anxiety. Here, this unpleasant 

 business is dispensed with, and the anxiety too, as well as the 

 sitting up till the house is heated and safe for the night. You 

 go to the tank or box, which is generally situated so as to be 

 easily got at, in a recess made in the wall, perhaps, or immedi- 

 ately over the boiler, as represented in Fig. A ; but, in any case, 

 it should be so arranged as to be alwaj'-s of easy access from the 

 houses. The arrangement of the pipes makes no difference, 

 providing the accumulating tank be sufficiently elevated. The 

 moment the water is put on, the circulation commences; in 

 flows a delightful stream of hot water, warming the pipes as it 

 proceeds through the flow and return ; a vivifying glow of 

 warmth pervades the chilly atmosphere of your green-house, and 

 you can retire to rest without being troubled with anxious 

 thoughts about your plants, let the weather turn as it may. 



It may appear, that, by this arrangement, a larger quantity of 

 fuel will be required for a single house, than if that house had 

 an apparatus for itself. Not so, however ; for, by close observa- 

 tion, it is found that the consumption of fuel is pretty nearly in 

 proportion to the water heated, and that the heat given off by 

 the pipes is in direct ratio to .the heat absorbed by the boiler 

 from the fire. Thus, if one house only be at work, there is only 

 the water of one arrangement to be heated ; and, consequently, 

 only one return of cold water into the boiler, the rest being shut 

 ofT. Now, if the water be shiU ofT into the box, that is, the 

 mouths of the flow-pipes stopped, there is no circulation ; hence, 

 there is no return of the cold water into the boiler, and, conse- 

 quently, no absorption of caloric or combustion of fuel. Of 

 course, more fuel is required to heat the four houses, than would 

 be required to heat one, for the reasons stated, that the larger 



