As may be surmised vast quantities of wood and of wood-producing land are required for extensive charcoal manufacture, and this is the most serious problem for the manufacturer of charcoal. Several square miles of timber land must be cut over each year and the wood efficiently transported in order to operate a large plant profitably. Pig iron as a _by-product_ is a rather novel idea, but that is practically what the charcoal pig iron produced in our Lake Superior region is. Several companies operate wood distillation plants for the production of methyl alcohol, acetic acid, acetate of lime, etc., and use their charcoal in the manufacture of charcoal pig iron from the ores so close at hand. The very low sulphur content and the small amount of ash have been the great advantages possessed by charcoal over other solid fuels. Resulting characteristics made charcoal pig iron a former favorite for manufacture of certain articles such as chilled car wheels, etc., and it, therefore, brought a higher price than coke pig iron. During recent years, however, by careful selection of coal and improvements in the coking process the sulphur and ash of coke have been so reduced that charcoal has not so great an advantage as formerly. Charcoal iron to-day brings only about $1.50 per ton more than coke iron; whereas, the differential a few years ago was as great as $5.00 or $6.00 per ton. Charcoal is quite fragile and structurally weak, so much so that blast furnaces for its use cannot be built higher than sixty feet; whereas, the great strength of coke allows them to be built to exceed one hundred feet in height with correspondingly increased output. What this means may be realized by every one conversant with the demands of modern industry. Coke [Illustration: CHARGING COAL INTO THE OVENS ] As charcoal is completely charred wood, so coke for analogy’s sake may be said to be completely charred coal, practically always of the bituminous type. By “baking” bituminous coal at a cherry-red heat, its volatile constituents are driven off as the well-known “coal-gas” of almost every small town, and a strong, brittle and porous material or coke residue is left. If the baking is done without any admission of air to the retort, practically none of the coal burns and the “cake” or coke which is left contains the ash of the original coal and what is known as the “fixed carbon,” i.e., carbon which cannot be distilled or driven off by heat alone, though it would burn were air admitted. The gases or volatile constituents which are given off consist mainly of moisture and a mixture of gaseous chemical compounds, which are known as “hydro-carbons.” These contain that part of the carbon of the original coal which does not remain as “fixed carbon” in the coke. [Illustration: QUENCHING AFTER COAL HAS BEEN COKED ]