“Merely to use in making hydrochloric acid,” wrote the earth-man in reply. “And that?” “To use in making sal ammoniac for my batteries.” “Do you need nitric acid for anything except the manufacture of sulphuric?” “No.” “Then,” Doggo suggested, “let us make our sal ammoniac directly from its elements. We shall build a series of about twenty vertical cast-iron retorts, as soon as you have smelted your iron. These we shall fill with damp salt, pressed into blocks and dried. We shall heat these retorts with charcoal fires, and through them we shall pass then, air, and the sulphur fumes of your ore-roasting. “After about fifteen days we shall daily cut out the first retort, dump out the soda which has formed in it, refill it, and place it at the farther end of the series. The liquid, which condenses at the end of the series, will be diluted hydrochloric acid. By passing the fumes of roast animal-refuse through it we shall convert it into sal ammoniac solution.” Accordingly, the quicker they started their foundry operations, the better. By this time chalcopyrite, quartz, and charcoal were present at Vairkingi in large quantities. The ore was first roasted, and then was piled into the smelter with the quartz and charcoal; the air-bellows were started, fire was inserted through the slaghole, and soon a raging pillar of flame served notice on all Vairkingi that the devil-furnace of the great magician was in full blast. By this time it was night, but no one thought of stopping. Of course, there were complications. The furry soldiers deserted the pumps at the first roar of green-tinged flame, but Doggo instantly stepped into the breach and operated all of the bellows with his various legs. Finally the warriors, on seeing that Myles and Quivven had survived the ordeal of fire, sheepishly returned to their posts, and were soon loudly boasting of their own bravery and of how their fellows would envy them on the morrow when they should relate their experiences. Along toward morning Cabot drew his first heat of molten matter into a brick ladle and poured it into the converter. It was an impressive sight. The shadowy wooden-walled inclosure, lit by the waving greenish flare of a pillar of fire, which metamorphosed the white skin of the earth-man into that of a jaundiced Oriental, tinged Quivven with green-gold, and glinted off the shiny carapace of Doggo as off the facets of a bloodstone. In the darkness of the background, toiled the workers at their pumps. Then there came a change. The fires died down, the pumping ceased, oil lamps were lit, and the ghostly glare gave place to a faint but healthy light, although over all hung the ominous silence of expectancy. The ladle was brought up, a hand-hole-cover removed, and out flowed a crimson liquid, tinting all the eager surrounding faces with a sinister ruddiness.