374 On the relative Proportions of Coals and 
ereafe, and always in proportion to this increafe will the 
fufibility and value of the iron be mended.- From the whole 
an important leffon may be learned of the pernicious effeéts 
of water in the furnace, and how abfolutely neceffary it is to 
prepare the cokes without ufing water, either to damp the 
fires, as in the ufual mode, or to cool the cinders obtained 
from the tar kilns, to prevent their confuming in the open 
air: in all this hurtful operation confiderable quantities of 
water become fixed in the cokes, which require a very great 
degree of heat to expel. 
THE preparation of iron-ftone has already been fully at- 
tended to, and the phenomena which it exhibits under every 
ftage minutely defcribed. In confequence of various expe- 
riments we are authorifed to draw the following conclufions : 
That when pure calcareous iron-ftone is ufed, it admits of hay- 
ing the local quantity of cokes diminithed ; that argillaceous 
requires a larger portion than the calcareous genus; and that 
filiceous iron-fione requires a greater proportion of fuel than 
any variety of the former genera. ° We have alfo feen that 
fafibility, either conneéed with ftrength or otherwife, is de- 
rived from the mixture of the ores; and that exceflive brittle-. 
nefs, intimately conneéted with infufibility, is alfo derived 
from the fame fource. From a review of thefe faéts, we are 
forcibly impreffed with the importance of combining the pre- 
pared iron-fiones with proportions of fuel fuited to their va- 
ious natures, in order.to produce all the varieties of crude 
iron with the greateft poflible ceconomy. Contemplating 
farther the fame fubject, it is eafy to be conceived that a 
want of knowledge of the component parts of iron-ftones, 
and the effects which individually they produce, muft lead 
to great uncertainty of operation in the fmelting procefs, 
wherein the beautiful ceconomy of nature, and even real 
property, will be often unprofitably facrificed to precedent. 
Befides the above caufes of alteration, dependent upon 
mixtures of the ‘earths, the exiftence of oxygen in various 
quantitics in the ores ought never to, be overlooked in pro- 
portioning the cokes to the iron-ftone. “This powerful agent, 
whole 
