. 12.] EXPLANATION OF THE PLATES. 23! 



laid down by a large fcale, which, I hope, 

 will be found legible to, and underftood by 

 every operative perfon, without the minu-* 

 tiae of explanation. But i remains for 

 me to give fome directions for the work- 

 ing of it, and to defcribe that which con- 

 ftitutes its principal difference from the 

 common fur . ce 



In the common hot-houfe furnace, the 

 grate occupies the whole fpace allowed 

 for the fuel/; and is alfo generally placed 

 on a level with the bottom of the flue, its 

 entrance being thereby eaiily choaked, 

 which occafions what is termed an ill- 

 drawing furnace. And where the bottom 

 pf the flue is elevated above the grate, the 

 confequence is worfe$ in which cafe, the 

 fire burns with fuch rapidity, that it is 

 hardly poflible to regulate the climate of 

 the houfe to the degree required ; befides, 

 there is a great wafte of fuel. 



This is obvioufly occasioned by there 

 being no fpace allowed for the fuel but 

 the furface of the grate, through which, 

 and confequently through the whole fire, 

 the current of air muft pals into the flue j 

 whereby it is fuddenly exhaufted, and the 

 P4 flue 



