pike Objervations on Iron and Steel. bf 
* Britain ; ‘and alfo-that chemical writers in general, from 
. neceflity as often as choice, confine their experiments 
‘imply to the laboratory: thefe, however accurate, will 
always be found materially varied when followed out on a 
large {cale. 
When M. Fourcroy ftates the length of time neceffary 
for cementing ftcel, moft evidently he alludes, not to fteel 
manufactured in the large way, but to that’ effected in 
chemical experiments; clfe, he never could have mentioned 
an earthen box. | It is well known that bars of iron {th of an 
inch in thicknefs, the length is no way material, will 
pafs into the ftate cf good fteel during 12 hours cementa- 
tion with a white heat. Had M. Fourcroy meant any 
other than bar /teel, he would not have mentioned iron as 
the fubftance to be operated upon. 
In regard to the time neceffary for cementing fteel on a 
darge feale, Mr. C. has ftruck the extreme from the chemical 
gentlemen whom he quotes, and who only give the refults 
from their laboratories. In the lengthened procefs of 16 
days, ftated by Mr. C. as being the requifite time for ce- 
menting malleable iron into fteel, he includes the time which 
the furnace is allowed to cool, before the workmen can 
penetrate to the contents ; and this period may be lengthened 
or fhortened from local circumftances. The procefs, P pre- 
fume, is reckoned complete when the iron is deemed fuf- 
ficiently faturated with carbon: this is judged of by the trial 
‘ars: if thefe are found perfect, then the whole converfion 
will be in a fimilar ftate: fhould the furnace after this re- 
main a month unempticd, this adds nothing to the real 
length of time neceflary for cementation: I have feen 
feveral inftances, where the workmen have emptied the 
furnace of high converted fieel, for drawing into German 
fteel, upon the 11th day. 
It would be a very difficult matter for Mr. Collier to point 
out any greater advantage which fteel poficffes,’ than that 
noticed by Mr. Nicholfon ; namely, its property of becom- 
. ing 
