453 



3'"'. Prevents aridity conséquent upon radiation and condensation 

 in bright cold weather either day or night. 



4th . Almost total cessation of anuoyance by insects. 



ExMnples of advmitages. 



1*'. In hot summers the beat bas never gone up bigber tban 70° 

 with a single roof, only one bot morningwould bave run it up to 85". 



2"". The cubic contents of tbe bouse is 46,000 feet. Tbe beating 

 power is only 430 feet of 4 incbes pipe or about, 1 footof pipe to every 

 100 cubic feet of air. Tbis quantity of pipe in a single roofed bouse 

 would only just keep out frost, but witb the double roof it rarely goes 

 down below 48**. Tbe estimate is a gain of 14° of beat. Tbe loss of 

 beat is very slow in cold weather. It would take 3 nights of severe 

 frost to bring tbe beat down from 52° to 48° and probably 36 bours 

 to cause the same réduction if tbe fires were to go out entirely. Witb 

 a single roof tbis réduction would take place in 6 bours. It is a great 

 comfort to know that if the fire was neglected or an accident happened 

 to the boiler in winter for a wbole night that tbe plants would receive 

 no damage. 



3''<î. Non radiation of beat througb tbe roof. In ordinary bouses 

 wbere moisture forms a requisite of good plant growing, no matter 

 bow freely we use the syringe in the evening, we find tbe bouse dry 

 in tbe morning, arising from the gi-eat condensation of moisture on 

 the roof and running off when thus condensed. Witb double roof 

 there is very little condensation on the l'oof, tbe blanket of non- 

 conducting air between tbe two roofs of giass preventing it; andcon- 

 sequently as the air cools down a little in the night, the condensation 

 takes place on tbe plants themselves, exactly according to nature. The 

 plants in the orchid bouse which bas a double roof and sides are in 

 the morning beautifully covered witb dew like a plot of cabbages in 

 a May morning. Is not tbis tbe perfection of plant growing.P There 

 is another fact connected witb non radiation of great importance in 

 plant growing. It is tbe curious fact, that there is a steady uniform 

 increase of température in the bouse according as we ascend from tbe 

 floor to tbe roof, day and night. Thus in tbe Fernbouse bardy ferns 

 and tena.perate plants grow below, while tropical ferns , plants and 

 palms grow near the roof. In ordinary bouses we remove tender 

 plants from near tbe glas s in severe weather; but in tbis double roofed 

 Fernbouse the nearer they are placed to tbe glass the warmer they are. 



The saving of fuel is 20 percent per annum, so that tbe extra cost 

 of tbe double roof is soon paid for in fuel alone, but tbis a trifle com- 

 pared to tbe enhanced value of the plants grown in a double roofed 



