HEATING GREENHOUSES. 193 



this can onl}' be attained with the least qnantit}^ of pipes to 

 accomplish the proper heating. 



Another veiy important point in construction is, that the radiat- 

 ing pipes should be continuous and without a break till they 

 again reach the end of the greenhouse wliere tlie boiler is situated, 

 gradually falling to this point so that no air will remain at anj' 

 point in the pipes when filled Avith water. 



A single pipe will cross the entrance end of the greenhouse on a 

 level with the door-sill, conducting the water directly to the boiler, 

 thus making a continuous circulation. 



The radiating pipes should be four in number, two inches in 

 diameter, of wrought iron, with screw joints. Tlie\- should be 

 painted black with a preptiration of oil and lampblack, for when 

 they are so painted tliey radiate more heat than if left in their 

 natural state, and they are also preserved from rust by this appli- 

 cation of paint. They should also be hung up one above the other 

 around the inside of tlie greenhouse clear of the wood-work and 

 the ground, so that all the heat radiated from the pipes will go to 

 heat the air in the house, instead of being absorbed by contact 

 with exterior masses. 



A greenhouse 100 feet long, 20 feet wide, and 10 feet high under 

 the ridge-pole, built half-span roof, with the longest roof facing 

 south, will require about 900 feet in length of 2-inch wrought iron 

 pipe. This would give a radiating surface of about 590 square 

 feet, amplj' sufficient to properly heat the house I describe. The 

 glass surface will be about 2,300 square feet, and the solid con- 

 tents of house about 15,000 cubic feet. The quantity of water 

 in the boiler and radiating pipes will be about 130 gallons. 



I wish to say a word in regard to the construction of the 

 grate under my boiler. I would make it of 1^-inch gas-pipe, 

 leading from a 4-inch pipe-head, which head can be extended 

 to take in fresh air. This fresh air will pass through the grate 

 into a conductor placed along one side of the greenhouse under 

 the radiating pipes. This conductor can be constructed of old 

 4-inch pipes, perforated with graduated holes the whole length for 

 the equal distribution of warmed air into the greenhouse. 



This is quite a novel idea, but one which will, I think, commend 

 itself to you as feasible, when you once reflect on the quantitj- of 

 heat wasted in the ash-pit, and which will be made to contribute 

 to heating the grate-bar pipes, through which a great quantity of 

 air must pass when these pipes are hot. At all times this grate 



