DETACHED GREENHOUSES, ETC. 177 



mated by glass surface, about one foot in length of four- 

 inch pipe is necessary for every three and a half square 

 feet of glass surface, when the temperature is at ten de- 

 grees below zero, to keep a temperature of fifty degrees in 

 the greenhouse. We now place all our pipes under the 

 side benches, as that enables us to use the space under 

 the middle for stowing away many plants safely, which 

 otherwise could not be done if the pipes were there. 



Heating greenhouses by steam is rapidly coming into 

 use, and, in my opinion, whenever the extent to be heated 

 is over five thousand feet of glass surface, steam should 

 be used in preference to hot water, for the reason that it 

 ought to be cheaper to put up, one foot of steam pipe 

 costing ten cents being equal to the hot-water pipe costing 

 twenty cents ; and, in addition, in a thorough compara- 

 tive trial we find it to be a saving of about twenty-five 

 per cent, in coal. As far as the well-being of the plants 

 is concerned, it makes no difference whatever whether 

 the greenhouse is heated by hot water or by steam. 

 There is an impression that the heat given off from 

 hot-water pipes is more moist than that from steam ; 

 but this is an error, as experiments show there is 

 no difference whatever. 



USING GAS TAR ON STEAM OK HOT-WATER PIPES. 



Every season some one is led into the grievous blun- 

 der of painting the hot-water or steam pipes with gas tar. 

 This never fails to result in the almost complete destruc- 

 tion of the plants as soon as the necessity for heating 

 the pipes begins. The heat evolved from the pipes so 

 painted gives out a gas destructive to all species of plant 

 life. When the blunder has been committed, there is no 

 remedy but to take out the pipes and burn the gas tar off 

 by a red heat. All kinds of remedies have been tried 

 again and again, and all have failed, for the reason that 



