The engineer proceeded in this manner. The sealskin bellows, furnished with a pipe of refractory earth (an earth difficult of fusion), which had previously been prepared at the pottery, was set up close to the heap of ore. And, moved by a mechanism consisting of a frame, fibre-cords, and balance-weight, it injected into the mass a supply of air, which, by raising the temperature, assisted the chemical transformation which would give the pure metal. The operation was difficult. It took all the patience and ingenuity of the colonists to conduct it properly; but finally it succeeded, and the result was a pig of iron in a spongy state, which must be cut and forged in order to expel the liquified gangue. It was evident that these self-constituted smiths wanted a hammer, but they were no worse off than the first metallurgist, and they did as he must have done. The first pig, fastened to a wooden handle, served as a hammer with which to forge the second upon an anvil of granite, and they thus obtained a coarse metal, but one which could be utilized. At length, after much trouble and labor, on the 25th of April, many bars of iron had been forged and turned into crowbars, pincers, pickaxes, mattocks, etc., which Pencroff and Neb declared to be real jewels. But in order to be in its most serviceable state, iron must be turned into steel. Now steel, which is a combination of iron and carbon, is made in two ways: first from cast iron, by decarburetting the molten metal, which gives natural or puddled steel; and, second, by the method of cementation, which consists in carburetting malleable iron. As the engineer had iron in a pure state, he chose the latter method, and heated the metal with powdered charcoal in a crucible made from refractory earth. This steel, which was malleable hot and cold, he worked with the hammer. And Neb and Pencroff, skillfully directed, made axe-heads, which, heated red-hot and quickly plunged in cold water, took an excellent temper. Other instruments, such as planes and hatchets, were rudely fashioned, and bands of steel were made into saws and chisels; and from the iron, mattocks, shovels, pickaxes, hammers, nails, etc., were manufactured. By the 5th of May the first metallurgic period was ended, the smiths returned to the Chimneys, and new work would soon authorize their assumption of a new title. CHAPTER XVI. THE QUESTION OF A DWELLING DISCUSSED AGAIN—PENCROFF’S IDEAS—AN EXPLORATION TO THE NORTH OF THE LAKE—THE WESTERN BOUNDARY OF THE PLATEAU—THE SERPENTS—THE OUTLET OF THE LAKE—TOP’S ALARM—TOP SWIMMING—A FIGHT UNDER WATER—THE DUGONG.