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temperature in the night be fixed at 50, 

 and 10*= are allowed lor winds, and the 

 external air is supposed to be at zero or 

 of Fahrenheit, then 1175 multiplied by 

 00, and the product divided by 2.1, the 

 difference between 200 and (50 will give 

 us the quotient 236 to the surface of 

 pipe required. Now, the house being 

 thirty feet long, five pipes of that length, 

 aud five inches in diameter, will be about 

 the -proper quantity. 



If hot water be employed instead of 

 steam, the following proportions and 

 infonnation, obtained from Mr. Kendle, 

 may be adopted confidently as guides : 

 In a span-roof propagating house, forty 

 feet long, thirteen feet broad, seven feet 

 high in the centre, and four feet high at 

 the two fronts, having a superficial sur- 

 face of glass amounting to 588 square 

 feet, Mr. Rendle has a tank eighty-three 

 feet long, running round three sides of 

 the house, four feet wide and about eight 

 inches deep, and consequently capable of 

 containing nearly 300 cubic feet of hot 

 water, though only half that quantity is 

 used. This is closely approaching to the 

 size pointed out, according to Mr. Tred- 

 gold's formula. The mean temperature 

 of a hot-water tank will never be much 

 above 100, so that, for the sized house 

 mentioned by that skilful engineer, the 

 divisor must be 2.1 times the difference 

 between 100 and 00, which gives as the 

 quotient 335 cubic feet. 



The tank in Mr. Rendle's propagating- 

 house is built lined with Roman cement, 

 and if the temperature at the time of 

 lighting the fire be 90, the temperature 

 of the atmosphere of the house 67, and 

 the temperature out of doors 50, the 

 quantity of small coal or breeze required 

 to raise the temperature of the water to 

 125 is 28 pounds. In twelve hours the 

 water cools, after the fire has been ex- 

 tinguished, from 125 to 93. 



When steam is employed, the space 

 for steam in the boiler is easily found 

 by multiplying the length of the pipe in 

 feet by the quantity of steam in a foot in 

 length of the pipe. 



In the above-noticed house, the length 

 of pipe five inches in diameter is 150 

 feet ; and these multiplied by 1.363=20.5 

 cubic feet of steam, and as the pipe will 

 condense the steam of about one cubic 

 foot and one-third of water per hour, 

 therefore the boiler should be capable of 

 evaporating If cubicfeetof water per houTi 



to allow for unavoidable loss. In the 

 extreme cases of the thermometer being 

 at zero, the consumption of coals to keep 

 up this evaporation will bo 12-J pounds 

 per hour. 



These calculations are all founded upon 

 the supposition that the condensed water 

 is returned to the boiler whilst hot ; but 

 if this cannot be effected, then one-twelfth, 

 more fuel will be required. The boiler 

 for the supply either of steam or hot water 

 should be covered with the best available 

 non-conductor of heat, aud this is either 

 charcoal or sand. 



A case of brickwork, with pulverized 

 charcoal between this and the boiler, is 

 to be preferred to any other. A boiler 

 having a surface of seventy feet exposed 

 to the air, in a temperature of 32, requires 

 an extra bushel of coals to be consumed 

 per day, to compensate for the heat 

 radiated and conducted from that surface- 

 and the smaller the boiler, the greater is 

 the proportionate waste. The surface oi 

 the pipes should be painted black, because 

 a surface of this colour gives out moro 

 heat in a given time than any other. 



Bark or Moist Stove. Mr. London 

 gives the following design and description 



of a moist stove, warmed on the old plan 

 of deriving heat by the combined agency 

 of bark and flues. Instead of a stage in 

 the centre it has a pit, which may be from, 

 two and a half to four feet deep, according 

 as bark or leaves are to be used, the latter- 

 material requiring the greatest depth. It 

 is commonly surrounded by a thin brick 



