120 SEVENTH REPORT—1837. 
it lost rather more than half its weight. The matter driven off 
by coking constituted in fact a most important part of the fuel, 
being the substances now well known under the names of coal- 
gasand naphtha. By diminishing the force with which the air 
was driven into the furnace, and by taking care that thisair should 
be dry instead of moist, (in consequence of the water pressure 
originally employed,) and by some other minor improvements, 
the consumption of coals was reduced from 10 to 8 tons, or 
rather to 7 tons 13 cwt. for the production of one ton of cast iron. 
The quantity of limestone employed for smelting a ton of 
cast iron was 105 cwt. 
In the year 1833, when the mode of heating the air was 
brought to a state of tolerable perfection, and when the tempe- 
rature of the air introduced was considerably above 607°, as it 
melted lead at the distance of an inch from the orifice, and the 
melting point of lead is known to be 607°, at that time coal 
was employed without being previously coked, and the quantity 
requisite for smelting a ton of cast iron was 2 tons 19 cwt., 
namely, Tons. Cwt. 
For the furnace’:.) -) wr... 2 0 72250 
For heating theair . . « . »« . O 8 
For the steam engine . . .. . Oll 219 
The quantity of limestone used was reduced from 103 to 7 
cwt.; and the product in iron was greater, and the daily quan- 
tity produced from a furnace was increased from 6 tons to 9 tons. 
The expense of a ton of cast iron was in 
ASQOM HY WS hee. wid SEA 
TESS! AE a ah int at ot QED 
Produce in a month from 3 furnaces in 
$8294 iene ts |. oS) 600, tons esata 
TVBSS>. ao Wee Pod oot ov) 2 1010 : 
When the Clyde iron works were originally established two 
furnaces produced only 14 tons of cast iron weekly. The pro- 
duce was gradually increased to 30, 40, or even 70 tons a week ; 
but after the introduction of the heated air the produce was as 
much as 130 tons a week. Indeed it was raised to almost 200 
tons a week, but that was by the addition of another furnace. 
Various explanations have been given of the way in which 
the heated air acts to produce these advantages. If we attend 
to the facts which I have just stated the true explanation will 
I think easily suggest itself. 
When iron is smelted by the cold blast the coal requires to 
be coked, but when the hot blast is employed coking is unne- 
cessary. In the latter case one half the quantity of coals is suf- 
ficient that is required in the former. Is it not evident from 
this that the whole oxygen of the air of the hot blast combines 
ea i el id ig ee 
