26 



greenhouse plants generally. During the resting 

 season of orchidaceous plants, the atmosphere of the 

 house is easily kept less humid, by not removing the 

 whole or any part of the lids. 



For vineries and peach-houses, it would answer 

 exceedingly well, and entirely eradicate the red spi- 

 der ; for the trough can be covered when the trees 

 are in flower, and when the fruit is approaching 

 towards maturity. On the other hand, during the 

 growing season you may maintain a regularly humid 

 atmosphere with less trouble than by any other 

 means. In a pine-stove, forty feet long, with a walk 

 between the back wall and bark bed, the trough being 

 two feet from the level of the walk, Mr. Griffin says, 

 ' I can command any degree of heat with much less 

 attention than is required for some houses with a 

 boiler of the same description and equal power as re- 

 gards pipe.' (Gard. Chron.) 



Heating by Steam. — If this be employed, Mr. 

 Tredgold has given the following rules for calculating 

 the surface of pipe, the size of the boiler, the quantity 

 of fuel, and the quantity of ventilation, required for a 

 house thirty feet long, twelve feet wide, with the 

 glass roof eight feet, length of the rafters fourteen 

 feet, height of the back wall fifteen feet. The surface 

 of glass in this house will be seven hundred and 

 twenty feet superficial, viz., five hundred and forty 

 feet in the front and roof, and one hundred and eighty 



