846 Report of the Committee 
3<ily, Care muft be taken to flop up the hole in the 
cover through which the tube is inferted, and to make 
the cover fit pretty clofe, fo that no air fhall enter into 
the pot that way, and that not much fleam may efcape. 
A piece of thin flat tin plate muft alfo be laid on the 
mouth of the chimney, fo as to leave no more paflage 
than what is fufficient to carry off the fleam. The fize 
of this plate fliould be not much more than fufficient to 
cover the chimney, that its weight may not be too great ; 
and the mouth of the chimney fliould be made flat, that 
the plate may cover it more completely. It muft be ob- 
ferved, that when the tin plate is laid on the mouth of 
the chimney, it will commonly be lifted up by the force 
of the fleam, and will rattle till it has flipped afide fuffi- 
ciently to let the fleam efcape without lifting it up. In 
this cafe it is not neceflary to put the plate back again, 
unlefs by accident it has flipped afide more than ufual. 
If the artift pleafes, he may tie each corner of this plate 
by a firing to prongs fixed to the chimney, and Handing 
on a level with the plate, as thereby it will neceflarily be 
kept always in its place (I> \ but we would by no means 
recommend having it made with a hinge, as that might 
(l) Fig. 3. is a perfpe£live view of the chimney and tin plate; abcd is the 
plate; E the chimney; f/, G£, Mm , and Kn , the prongs fattened to the chim- 
ney, to which the four corners of the plate are to be tied by the firings af, bg, 
cm, and dn; the ends f, g, m, and n, of the prongs muft be on a level with 
-the plate, and the firings fhould not be ftretched tight. 
5 
be 
