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ill. On the various Effcds produced by the Nature, Cotn- 

 firejfion, and Velocity of the Air uj'ed in the Blaji- Furnace. 

 By Mr. David Mushet, of the Clyde Iron-Works^ 

 Communicated by the Author. 



I 



[Concluded from Page 70.3 



HAVE explained the neceflity of jaft proportions exifting 

 betwixt the area of the interior of the blaft-furnace, the 

 quantity of air thrown in per minute, and the quaUty of 

 coal. The various modes of hlowng, and their refpedlive 

 cffefts, deduced from ftrift obfervation, v/tre alfo attended to. 

 We have now, 3d, to adduce examples Aviiere the various 

 changes of the atmofphere, as to heat and preflTure, oceafioii 

 the molt fenfible difference in the quantity of materials con- 

 fumed, and in the quality and quantity of metal produced. 



It has been already dcmonftrated, that the air in winter, 

 by containing lefs moifture, is more proper for combullion, 

 and more calculated to produce carbonated crude iron, than 

 the air exifting at any other feafan. From this fuperior 

 quality the Tnanufa6lurer obtains advantages, which induce 

 him to wirti for a continuance of cool air throughout the . 

 whole year, Tiiefe effefts are not, however, uniform ; they 

 depend greatly upon a light or heavy atmofphere. The 

 keener and more (till the air, the more rapid the combuf- 

 tion. During a feverc froft, the dcfeent of the materials is 

 facilitated from ~ to ,-y more than in rainy or hazy wea- 

 ther, and at the fame time the quality of the iron is rather 

 improved than impaired. When a change from froft to fnow 

 or rain takes place, the cfl'e6ls frequently become almoft im- 

 mediately obvious : the colour of the flame at the furnaccr 

 head is changed ; the tuvre of the furnace inflames, and burnj 

 with great violence ; the lava, as it flows from the notcl] of 

 the dam-ftone, becomes lengthened and tenacious ,• the form 

 of it is changed, and the colour undergoes the moft vifible 

 Iterations; the iron no longer retains its complete faturation 

 r/f carbon, but flows out fenfiblv impaired of its fluidity, 

 and, when cold, the privatioii of carbon is mod evident by 

 the examination of its fracture. 



VoL.Xl. a When 



