DESCRIPTION OP HOTHOUSES. 135 



Mr. Stewart felt very desirous to grow pines 

 without the aid of tan, and with more steam 

 than he had hitherto been able to do. He there- 

 fore got a pit, in which he built two flues, and 

 supported over them, on brick props, a flooring 

 of pavement, covered with a layer of gravel and 

 sand on which to place the pots ; at the sides 

 were openings, to admit the heated air from 

 below, to warm the atmosphere of the plants ; 

 the upper level of the platform, on which the 

 plants stand, is nearly on a level with the exter- 

 nal surface. The pots of plants are set on the 

 sand, so that when moisture is added either to 

 it or to the plants, it causes a fine gentle steam 

 to arise through the whole of the pit, which can 

 be regulated at pleasure, by adding more or less 

 fire, according to the season or other circum- 

 stances." After nearly three year's experiences 

 Mr. Stewart is " fully convinced" that tan is 

 quite unnecessary, not only as a source of bottom 

 heat, but even for rooting the crowns and suck- 

 ers. " The temperature kept during the spring 

 and summer is from eighty to one hundred de- 

 grees through the day, and as low as from sixty- 



