380 On the AJfayhig of Ores hj Vujion. 



and may at all times be ufcd without inconvenience, and 

 almoft without being obfened. 



I fhall certainly make trial of it in the firft cafe that 

 occurs. 



XI. On the Affaring of Ores by Fufion. By Mr. David 

 MusHET of the Clyde Iron IVorks. Communicated by the 

 Author, 



JVXy Paper in the Number for July concluded with a 

 table of the proportions requifitc to obtain, from all the va- 

 rious iron-ftoncs, an accurate alfay ; the perfeftion of which 

 is always indicated by the fuperior tranfparency of the flux, 

 and the fuper-carbonation of the metallic button. By fcru- 

 puloufly following thefe and finiilar proportions as tlic exi- 

 gencies of the ore may point out, crude iron will always be 

 obtained of the finell quality, carbonated beyond whatever 

 is produced in the large way of manufa£lure, and its furface 

 covered with a beautiful carburet of iron, either iix fmall 

 fliining fpecula, or in the ftate of a thin membrane. By 

 a fliorht gradation of change in the proportions of the com- 

 ponent parts of the flux, the metal of the fame iron-ftone 

 jnay be made to pafs through all the inferior llatt's. 



Since, then, all iron-ftones in the aflay-furnace may be 

 made 10 give out their iron at pleafure, of all the various 

 qualities, it is furely erroneous to aflcrt, that fuch and fuch 

 iron-fl;ones cont lin inch and fuch qualities of iron; that this 

 one affords metal of the tineft quality, while that, on the 

 contrary, yields iron fit onlv for forge-pigs or ballaft; yet thi* 

 is the univerfal language in the manufactory. In this, as 

 in many inftanccs, we accximmodate the language to our 

 ideas, rather than our ideas to truth. Tlie fuflVage of pre- 

 vailinsr cuftom has imperceptibly alfocialed with our ideas 

 many abfurdilies which we are afterwards aOiamed to ac- 

 knowledge, and which darken the gleam of truth, or render 



it 



