CHEMICAL SCIENCE. 219 



coincidence in every case the fact of its invariable coexistence with carbon, 

 wherever steel is produced, is incontrovertible. 



We have it on the old ordinary cementation-boxes, which, filled with char- 

 coal and the imbedded iron, are closed, but not hermetically sealed, and still 

 sufficiently open to the inevitable permeation, through the excess of carbon, 

 of atmospheric air, yielding, by its oxgen, carbonic oxide, and to the steel, 

 nitrogen. We have it still more especially and obviously when, in this 

 cementation process, there is superadded to the charcoal some horn or 

 leather shavings, or animal charcoal, along, sometimes, with an alkali a 

 very old but not a generally used modification. We have it when the iron 

 for conversion is exposed in close vessels to the action of coal-gas, but in 

 which coal-gas, to a greater or less extent, there is always present either 

 cyanogen or ammmonia, or both. We have it also on all the multifarious 

 expedients of the steel-workers and steel tool-makers, resorted to to givo 

 increased hardness to the metal ; that is, to eifect its most complete conver- 

 sion into steel; as, when the file-maker coats his file, before tempering it, 

 with a composition of cow-dung or with pig-flour two favorite specifics, 

 and both highly azotized substances, which he thinks useful merely for pro- 

 tecting the sharp angles of his cuttings from the action of the fire, but which 

 act, in reality, as well in more completely steelifying his finished work. We 

 have it in the use, in so many cases, of horn shavings, of horn dust, of 

 leather shavings, and of other animal, and consequently azotized, matters of 

 various kinds, in the use of other vegetable substances (besides that just 

 mentioned) containing large proportions of gluten, and consequently of 

 nitrogen ; in the use of the ammoniacal salts, to say nothing of the prus- 

 siates, the recognition of the potency and of the great value of which for 

 steel-making in bulk, as well as for merely hardening it superficially, as 

 heretofore, is now becoming general. 



We have a conspicuous instance of the eifect of the presence of this ele- 

 ment in a well-known fact, that, whilst the dipping of the hot metal into 

 olive-oil fails, the use of beef suet (an azotized fat) succeeds in giving to the 

 iron a coating of steel. 



It was the presence (but, to him, the unconscious one) of this same element 

 that gave to the celebrated expedient of Mr. Heath its chief potency, in 

 improving the quality of inferior steel, and not solely to any purifying or 

 alloying action (if any) of his manganese; for latterly Mr. Heath used coal- 

 tar, placed in contact with the steel, to reduce his manganese oxide ; and 

 this coal-tar is a highly nitrogenized as well as a carbonized compound. In 

 short, in whatever practice the various and continual trials of the steel 

 artisan may result, in his searchings after the best hardening agents (and 

 he resorts to the most extraordinary things), that practice will be found 

 invariably, when successful, to involve the employment of some material in 

 which nitrogen is an essential element. 



A review of the above facts and phenomena is provokingly suggestive that 

 the existing theory of the composition of steel is a wrong one. And the first 

 suspicion is that this nitrogen element does actually enter into and exist in 

 that compound; and that not to errors in analysis, but to misconceptions 

 when nitrogen was found in steel, or to the influence of preconceived 

 notions, are to be attributed the fact of this element exercising any kind of 

 agency in steel-making, having hitherto been overlooked ; or that its pres- 

 ence, when found, has either been disputed, or attempted to be accounted 

 for on other grounds than that of chemical combination. 



