C* J2-] EXPLANATION, OF THE PLATES. 237 



weather, and in funfhine allows of a larger 

 portion of frefh air, and of keeping up the 

 temperature at the fame time, which is cer- 

 tainly a great objed: in forcing. Befides, 

 it is furniflied as cheap as the common. 



The price of the fuperficial foot of glais 

 varying according to the fize of the fquares,, 

 it is of importance not to make thefe too 

 large; for inflance, a fquare which is 

 twelve inches on the fide, and which con- 

 tains ju-ft a foot of glafs, is fold at ten- 

 pence ; (I fpeak of third crown) $ whereas, 

 two fquares eight and a half by eight and 

 it half inches each, and which contains the 

 fame quantity to a mere fraction, is fold at 

 fixpence halfpenny. So that the fmaller 

 the fquare, the cheaper is the fuperficial 

 foot of glafs ; and this is occafioned by the 

 fmall fquares being cut from the broke or 

 wafte of the large ones, which, if the ma- 

 nufacturer has no market for, he is under , 

 the neceility of re-melting. 



From the above, I would not wifli to in- 

 fer that the fquares fliould be made too 

 fmall, as thereby the roof would not only 

 be darkened by too many laps, but there 

 would be too many aflragals in the faili \. 



and 



