NEW METAL IN CRUDS ?LA,T.XNA, &C, 



^19 



1 have conftru6ied a wind furnace here, which is in fotne re- Chemical fur- 

 fpeds to be preferred to the ufual form. The fides, inftead of of acone, nar- 

 being per'pendiciiIar,areinverted,ro that the hollowfpace is py- roweft above. 



•J- t A. XT- J.. 1 • • r- ■ , r Its g.eat advatt- 



ramidical. At the bottom the openmg is thirteen inches Iquare, tage is that the 

 and at the top but eight. The per- fueldefcends 

 pendicular height is 17 inches, o^^f^jring* ^^ 

 This form appears to me to unite 

 the following advantages. Jft. A 

 great furface is expofed to the air • 

 which, having an eafy entrance, 

 rufhea through the fuel with great 

 rapidity. 2d. The inclined fides 

 aft in fome meafure as re verberating 

 furfaces: And 3d. The fuel falls of 

 itfelf, and is always in clofe con- 

 tact with the crucible, placed near 

 - the grate. This I believe to be the principal advantage. The ' 



late Dr. Kennedy of Edinburgh, whofe opinion on this fubje£t 

 claims the greateft weight, found that the firongefi heat in our 

 .common wind furnaces was within two or three inches of the 

 ^rate. That therefore is the moft advantageous pofition for 

 >; the crucible, and dill more fo when we can keep it furrounded 

 ^with fuel. It is inconvenient and dangerous for the crucible 

 j ';^lo flir the fire often to make the fuel fall, and the pyramidical 



reform renders this unneceflary. It is al(b more ea(y to avoid a 

 fudden bend in the chimney by the upper part of the furnace 

 advancing as in this conftrudion. a is a grate; c and c are 

 two bricks, which I can let in at pleafure to dirainifh the ca- 

 pacity ; b is another grate, which I can place upon the bricks 

 c and c for fmaller purpofes ; d and d are bricks which I can 

 place upon the grate b to diminifti the upper capacity, fo that 

 in fad I have four different fizes in the fame furnace. I have 

 had forae very ftrong fires in ufing the whole capacity from the 

 grate a to the top e without the bricks c and c ; but I am at a 

 lofs for our good Englifli coaks. The bricks have all been 

 ground down to the flope of the furnace and fit in with toler# 

 able accuracy. They are totally independent of the pyramid 

 dical form, &i.c, of the furnace. 



4ii99unt- 



