To this earth succeeded two feet of fine sand, which was carefully laid aside as being valuable for serving the casting of the inner mould. After the sand appeared some compact white clay, resembling the chalk of Great Britain, which extended down to a depth of four feet. Then the iron of the picks struck upon the hard bed of the soil; a kind of rock formed of petrified shells, very dry, very solid, and which the picks could with difficulty penetrate. At this point the excavation exhibited a depth of six and a half feet and the work of the masonry was begun.
At the bottom of the excavation they constructed a wheel of oak, a kind of circle strongly bolted together, and of immense strength. The center of this wooden disc was hollowed out to a diameter equal to the exterior diameter of the Columbiad. Upon this wheel rested the first layers of the masonry, the stones of which were bound together by hydraulic cement, with irresistible tenacity. The workmen, after laying the stones from the circumference to the center, were thus enclosed within a kind of well twenty-one feet in diameter. When this work was accomplished, the miners resumed their picks and cut away the rock from underneath the wheel itself, taking care to support it as they advanced upon blocks of great thickness. At every two feet which the hole gained in depth they successively withdrew the blocks. The wheel then sank little by little, and with it the massive ring of masonry, on the upper bed of which the masons labored incessantly, always reserving some vent holes to permit the escape of gas during the operation of the casting.
This kind of work required on the part of the workmen extreme nicety and minute attention. More than one, in digging underneath the wheel, was dangerously injured by the splinters of stone. But their ardor never relaxed, night or day. By day they worked under the rays of the scorching sun; by night, under the gleam of the electric light. The sounds of the picks against the rock, the bursting of mines, the grinding of the machines, the wreaths of smoke scattered through the air, traced around Stones Hill a circle of terror which the herds of buffaloes and the war parties of the Seminoles never ventured to pass. Nevertheless, the works advanced regularly, as the steam-cranes actively removed the rubbish. Of unexpected obstacles there was little account; and with regard to foreseen difficulties, they were speedily disposed of.
At the expiration of the first month the well had attained the depth assigned for that lapse of time, namely, 112 feet. This depth was doubled in December, and trebled in January.
During the month of February the workmen had to contend with a sheet of water which made its way right across the outer soil. It became necessary to employ very powerful pumps and compressed-air engines to drain it off, so as to close up the orifice from whence it issued; just as one stops a leak on board ship. They at last succeeded in getting the upper hand of these untoward streams; only, in consequence of the loosening of the soil, the wheel partly gave way, and a slight partial settlement ensued. This accident cost the life of several workmen.
No fresh occurrence thenceforward arrested the progress of the operation; and on the tenth of June, twenty days before the expiration of the period fixed by Barbicane, the well, lined throughout with its facing of stone, had attained the depth of 900 feet. At the bottom the masonry rested upon a massive block measuring thirty feet in thickness, while on the upper portion it was level with the surrounding soil.
President Barbicane and the members of the Gun Club warmly congratulated their engineer Murchison; the cyclopean work had been accomplished with extraordinary rapidity.
During these eight months Barbicane never quitted Stones Hill for a single instant. Keeping ever close by the work of excavation, he busied himself incessantly with the welfare and health of his workpeople, and was singularly fortunate in warding off the epidemics common to large communities of men, and so disastrous in those regions of the globe which are exposed to the influences of tropical climates.