THE FORCING GARDEN. 



519 



iron one over the reservoir, and is used to regulate the tem- 

 perature of the house. 



The section of a vinery heated by hot water will give a 

 pretty good idea of the principle upon which it acts : («) is a 

 boiler two feet and a half long, eighteen inches wide, and 

 twenty inches deep, and placed in a niche in the back wall of 

 the house ; from the end of the boiler proceed horizontally 

 three cast-iron pipes, of four mches diameter; two of them 

 are joined to the boiler near the top, and proceed upon a level 

 to the front of the house, and along the front to the farthest 

 end, where they empty themselves into a reservoir, or make a 

 turn by an elbow-joint in the pipe, as circumstances may direct. 

 In either case, the water is conveyed back again to the boiler 

 by a single pipe, which is placed directly under the two upper 

 ones, and enters the boiler near its bottom. The fire is fed 

 and managed from behind^ in the usual manner, in the back 

 sheds {by-^See Plate. 



VENTILATORS. 



Hot-houses built with fixed roofs require a different mode of 

 ventilating, than those which have the roof-sashes made move- 

 able ; all curvilinear houses, without incurring a great ex- 

 pense, belong to this class. The most approved method of 

 ventilating houses of that description, are by having apertures 

 formed in the front, or parapet wall, under each sash, of sizes 

 differing according to the magnitude of the house, or the pur- 

 poses for which such house is intended. These apertures are 

 furnished with wooden doors or lids, which are opened more 

 or less, and shut at pleasure, either individually or all at the 

 same time, by means of a sympathetic movement. The top 

 part of the back wall is also furnished with corresponding 

 apertures for the escape of heated or foul air, and are either 

 made to pass directly through the wall, or to turn upwards 

 through the coping, and are, in either case, also opened and 

 shut up by the same means. According to this plan, a body 

 of fresh air is constantly passing into the house from the front 

 ventilators, dui'ing the time they are open; while from the to)) 



