160 SILK GROWER'S GUIDE. 



purpose of heating hot houses. For this purpose tim- 

 bers should be laid on the ground, and on these planks 

 are placed, the whole a little descending, that the water 

 of condensation may drain off. On all sides it may be 

 enclosed by masonry of brick or stone, laid in suitable 

 mortar. The steam pipe is laid four inches above the 

 platform ; and over this, the whole area is filled to the 

 depth of three feet, with round stories, from three to six 

 inches in diameter ; on this smaller stones, gravel, sand, 

 and finally loam, may be placed, and the soil and struc- 

 ture are prepared for cultivation. The steam pipe may 

 be of any dimensions, the only difference is that in a 

 small tube or iron pipe, the steam issues with greater 

 force. The usual dimensions of the steam pipe, as 

 named, may be an inch in diameter. It contains per- 

 forations of one-tenth of an inch in diameter, for the 

 emission of the steam. These holes are eighteen inches 

 asunder at the end next the boiler, but diminish in dis- 

 tance, an inch to every sixteen feet, till they reach the 

 extreme end, which is closed. The heat is thus dis- 

 tributed uniformly from end to end. Generally the di- 

 rection of these holes is upwards, but some few are in 

 the bottom to drain off the condensed water. 



The steam requires to be admitted from the boiler 

 once in twenty-four hours, in the most severe weather, 

 and but once in two or three days in moderate weather ; 

 and then an hour or two is sufficient, or as soon as the 

 steam escapes from the safety valve, as this shews that 

 the stones have become so far heated that they will no 

 longer condense the steam. 



This system requires no night work. The mass of 

 stones being insulated and enclosed, will retain its heat 

 in. proportion to the dimensions of the mass, and for a 

 longer or shorter space of time. 



Cases of brick or stone masonry to serve as flues, 

 and filled with rubble stones, or pieces of brick, or 

 round stones, may be built around the sides, or within 

 the area of the apartments, which may thus be warmed 



