2^6 Di'fcripHon of an JJfay -furnace. 



dfeftcd, I had conrtruc'^cd the pyrometer wliich I am x\o\^ 

 about to defcribc. It can in ]io point of view be confidercJ 

 as an univerfai inftrunicnt, as its fcale will be entirely local, 

 and vary according to the conftruftion and exigencies of the 

 furnace : it poflelVes, ho\^•ever, this advantage, that after a; 

 fcale of comparilon is formed betwixt it and Wedgewood's, 

 in the manner delcribed in the explanation, the allayer can 

 at any time mark, with confidcrablc accuracy, the degree at 

 which an experiment is cficftcd, and compare it with the 

 degrees of that fcale ; and if the furnace and apparatus are 

 kept in proper repair, the rcfults will be confillent with for- 

 mer ones. 



Description o/' //'*? Fijrnace. 



A A (Plate V.) the pedcflal of brick-work on which the 

 flirnace is reared. B, the afli-pit. C, a view of the centra? 

 parts of the grate, with a knee two inches deep and four 

 inches fquare, for the purpofe of receiving a pedcflal of iire- 

 clav for fupportlng the crucible. DD, the fcftion of an iron 

 cylinder, which contains the brick-work, with flanges projeft- 

 ing inwards both at top and bottom : the upper flange con- 

 tains two grooves for Aiding the cover!, (made of caft iron;) 

 and the under one projcfts ib far as to form a fupport for the 

 bars of the grate. EE, the lining of the furnace, compofcd 

 of fire bricks. F, the fire-place, three feet deep, ten inches- 

 diameter at the grate, and diminilhing to nine inches at the 

 top. G, the flue or draught-hole, which communicates with 

 the chimnev. H, tho chimney (the top broken oft' to make 

 it come into the platc>, which fhould never be lefs than 30 

 feet high, and nine inches fquare in the paflage. K, an 

 oblong reftangidar plate, which projefts from the top of the 

 cylinder for the purpofe of fupporting tlie pyrometer. LL, an 

 iron box with a fquare bar of itcel, which, in expanding, afts 

 upon the lever at the dlllance of one incii from the fulcrum. 



The letters of the horizontal and vertical fcdion refer to 



the fame parts of the furnace. 



Desckip- 



