550 GEOLOGY OF OHIO. 
1.32 tons of limestone used, and leaves 0.18 tons to reduce carbonic 
acid from the ore reduction, and .03 tons for the iron. This .18 tons of 
earbon will reduce more than half the carbonic acid produced in ore 
reduction, but one-half at least will be assumed fe escape and furnish 
heat. The heat production will then be: 
1.4 tons carbon burned at tuyeres to carbonic oxide.................... 3,360 
One-half the heat produced by ore reduction ..........s..00s02seceeceeees 840 
Heat of blast, 8 tons at 550° centigrade (specific heat .24) ............ 1,056 
Totalsheat produced... .sccccoucc cccossccsosscosencecoorereceeaessoe 5,256 
This 1s based on the most unfavorable, possible working. It is 
probable that the analysis of the gases from any raw coal furnace would 
show more carbonic acid than has been allowed for, and hence, a greater 
excess of heat produced; this excess would certainly appear to be caused 
by the absorption of heat on coking. If this is true, the effect is not 
only to cause the use of more fuel, but by withdrawing heat trom the 
top of the furnace, it tends to make the heat production in the hearth out 
of proportion to that in the stack, and hence to make a hot crucible and 
silvery iron. 
It would hence appear, that the peculiar results obtained in raw 
coal smelting are at least partly explained from the character of the 
slags, and the fuel causing both a hot hearth and cold shaft, on account 
of bad heat distribution and too much ash. 
These considerations would point to the desirability of very hot 
blast for the raw coal furnaces, so as to lighten the amount of fuel 
burned at the tuyeres. Full figures relative to this are not at present 
attainable, but those given in the table certainly show a great advantage 
in very hot blast. 
There are several other questions as to smelting which are impor- 
tant, and upon which notes, obtained in the laboratory of the Survey, 
may throw light. 
The assumption has been made that all the phosphorus in the ore 
and charge went into the iron. To make sure of this, several slags 
were examined for phosphorus. 
The highest percentage in a series of 6 analyses was .009, or less 
than .01 of one per cent.; this slag was from a furnace producing a pig- 
iron with 0.70 per cent. phosphorus, and giving a very basic slag. 
The ashes of coals contain in all cases some phosphorus; samples 
