48 Obfervations on Iron and Sleet. 



made in that part of Yorkfhire is procured from ores fourth 

 in the neighbourhood, which are of the argillaceous kind* 

 but intermixed with a large proportion of foreign matter. 

 Thefe, however, are frequently combined with richer ores 

 from Cumberland and other places. The ore is firft roafled 

 with cinders for three days in the open air, in order to expel 

 the fulphureous or arfenical parts, and afterwards taken to 

 the furnaces, fome of which are conftructed fo that their in- 

 ternal cavity has the form of two four-fided pyramids joined 

 bafe to bafe ; but thofe mofl commonly ufed are of a conical 

 form, from forty to fifty feet high. The furnace is charged 

 at the top with equal parts of coal-cinder and lime-ftone. 

 The lime-done acts as a flux, at the fame time that it fup- 

 plies a fufficient quantity of earthy matter, to be converted 

 into fcoria?, which are neceflary to defend the reduced metal 

 from calcination, when it comes near the lower part of the 

 furnace. The fire is lighted at the bottom ; and the heat is 

 excited by means of two pair of large bellows blowing al- 

 ternately. The quantity of air generally thrown into the fur- 

 nace is from 1000 to 1200 fquare feet in a minute. The' 

 air pafles through a pipe, the diameter of which is from two 

 inches and a quarter to two and three quarters wide. The 

 comprefiion of air which is neceflary is equal to a column 

 of water four feet and a half high. The ore melts as it 

 pafles through the fire, and is collected at the bottom, where 

 it is maintained in a liquid date. The flag, which falls down 

 with the fufed metal, is let off by means of an opening in 

 the fide of the furnace, at the difcretion of the workmen. 

 When a fufficient quantity of regulus, or imperfectly re- 

 duced metal, is accumulated at the bottom of the furnace 

 (which ufually happens every eight hours), it islet off into 

 moulds, to form it for the purpofes intended, fuch as can- 

 non or pig iron. — Crude iron is diftinguiflied into white, 

 black, and grey. The white is the leaft reduced, and more 

 brittle than the other two ; the black is that with which a 

 large quantity of fuel has been ufed ; and the grey is that 

 9 which 



