C. 12.] EXPLANATION OF THE PLATES. 225 



the roof, than in the furface of the back 

 Vail, of any hot-houfe. 



The fafhes are all to be made moveabley 

 both up and down, for the admiffion of air 

 at top, bottom, and middle. 



In the plan of thefe houfes, I hrrve fhewn 

 no back-Hied } but, if one is not erected, 

 which in fome fitiiations may be very im- 

 proper, the Jiock-hole mould be inclofed 

 with a wall, arched over, and a trap-door 

 made to go down in manner of a fhip's 

 hold, over which, when not at w r ork, may 

 be laid a little mould, &c. for conceal- 

 ment. 



But where the appearance of the furnace 

 is immaterial, it is of no confequence whe- 

 ther it be covered over or not 3 as, if the 

 furnaces are built according to Fig. I. 

 Plate V. they will be found to draw well 

 in any fituation. 



Fig. 3. reprefents part of an efpalier rail 

 on an improved conftrudion. Here the 

 pofts are fet in blocks of {tone, which are 

 placed under the furface of the border ; 

 and, for durability, the ends of the pofts 

 are burned, and run in with pitch. 



P SEC. 



