IO A MANUAL OF 



furnace is built, in the simplest manner, of 

 brick ; and the fire and heat flue, through 

 which the draught and smoke pass, runs up 

 through the centre of the trench. Stakes, made 

 of 3 by 4-inch scantling, are driven along the 

 sides of the trench at intervals of eight feet, 

 and it is then boarded up on the inside of the 

 stakes to a height of three feet on the north or 

 back side, and two and one-half on the front, 

 which should be the south side, in order that it 

 may lie to the sun and be sheltered from the 

 north winds. The cross sleepers for the floor 

 should now be placed. Near the furnace, where 

 the pipes get very hot, the floor should be at 

 least twelve inches above the pipes, but after 

 getting twenty feet from the furnace it may be 

 gradually lowered to within two or three inches, 

 care being taken to keep the distance great 

 enough to permit a free circulation of air over 

 the pipes. Above the floor we are to have 

 space for six inches or more of soil, and eight 

 to sixteen inches between the soil and glass for 

 growth of plants. More than this amount 

 will be found unnecessary, and, in fact, dam- 

 aging, as the whole structure should be kept as 

 low as possible, in order to economize warmth. 

 The spaces between the side boarding and earth 



