Ib6 Propel ties of SUe/. — Flcat excited by Frlifk/i; 



For tlicy are turned by an extremely flow motion, with a tool fcledcJ from the general 

 ilock in the work-fliop, becaufe the greater number even of good gravers will not cut it. ' 



4. Thoi'e who forge fteel know that it is very eafily degraded in the lire. If a fmall 

 piece, for example, half a cubic inch, of grey crude iron be put into a common fire, and. 

 kept red-hot for about half an hour, and at the expiration of that time the heat be fuddenr- 

 ly ralfed to whitenefs by the bellows ; the internal or fteely part will break its way ^through 

 the external cruft, which is converted into common iron, and rendered much lefs fufible. 

 This cruft, or hollow fliell, may then be taken out of the fire. All fteel becomes degraded 

 in the fame manner, even by very careful heating. Caft-fteel, drawn into fmall bars, ex- 

 hil^its cloudy lines and veins on its furface when tried by an acid, which no doubt have been 

 produced during the heating and forging. 



5. Caft-flcel being made out of broken tools of every kind, cannot of itfcif poflefs a larger 

 jlofe of plumbago than the average quantity contained in thofe fteels. But the Englilh caft- 

 fteel is more fufible and more tender under the hammer than German fteel, or the fteel of 

 cementation ; which circumftances appear to indicate that it contains more plumbago : and-* 

 the truth of this induftion is confirmed by its exhibiting a much darker fpot than other 

 fteels, when tried by an acid. Chalut did not therefore make this kind of fteel when he 

 ufed glafs only for his flux. It cannot be doubted but that the flux of our manufafturers 

 muft contain charcoal, at leaft. If it be animal coal, which is moft probable, it will alfo con- 

 tain phofphorus ; an ingredient to which the fuperiority of this coal, in cafcThardening, 13 

 probably owing. 



6. Tenacity and hardnefs are very frequently confidered as if they were one and the 

 fame quality with regard to implements and tools, though they are certainly very diftinck 

 properties. Tenacity is the oppofite to friability or brittlenefs ; hardnefs is the oppofite 

 to foftnefs. It is probable that iron is more tenacious than fteel, and ifr-is certain that foft 

 fteel is more tenacious than hard. Where tenacity and no confiderable degree of hardnefs - 

 are wanting, as in fprings, the inferior fteels, or the compounds of fteel and iron, will afford ' 

 a more fafe, and confequently in many inftances more ufeful article ; but where hardnefs 

 and tenacity are both required, the leading quality of the fteel muft be its uniformity. C^ft 

 fteel is preferred in England to every other kind, not only for polifhed fteel-work and the 

 beft cutting tools, but likewife for cold chifels, and the hard gravers for turners in metal ; 

 in both which laft I have obferved, by confiderable experience, that the common opinion is 

 well founded. 



III. 



yin Enquiry concerning the Source of the Heat which is excited hy Frisian*. By BENJAMiNi 

 Count of RuMFORD, F.R.S. M.R.I. J. 



At frequently happens that, in the ordinary affairs and occupations of life, opportunities 

 prefent themfelves of contemplating fome of the moft curious operations of nature ', and 



• From the Philofophical Tranfaftions, I798.~-Read January 25, 1798. 



Tcry 



