A single glance was enough to show him the chief purpose to which the chamber was devoted. The wall at one end was covered with arm-racks containing all the newest and most perfect makes of rifles and pistols; while at the other end, about twenty paces distant, were three electric signalling targets, graded, as was afterwards explained to him, to one, three, and five hundred yards range. In a word, the chamber was an underground range for rifle and pistol practice, in which a volley could have been fired without a sound being heard ten yards away. It was here that the accuracy of the various weapons invented from time to time was tested; and here, too, every member of the Circle, man and woman, practised with rifle and pistol until an infallible aim was acquired. A register of scores was kept, and at the head of it stood the name of Radna Michaelis. A long table ran across the end at which the arm-racks were, and on this Arnold laid the case containing the model, he standing on one side of the table, and the members of the Circle on the other, watching his movements with a curiosity that they took no trouble to disguise. He opened the case, feeling something like a scientific demonstrator, with an advanced and critical class before him. In a moment the man disappeared, and the mechanician and the enthusiast took his place. As each part was taken out and laid upon the table, he briefly explained its use; and then, last of all, came the hull of the air-ship. This was three feet long and six inches broad in its midships diameter. It was made in two longitudinal sections of polished aluminium, which shone like burnished silver. It would have been cigar-shaped but for the fact that the forward end was drawn out into a long sharp ram, the point of which was on a level with the floor of the hull amidships as it lay upon the table. Two deep bilge-plates, running nearly the whole length of the hull, kept it in an upright position and prevented the blades of the propellers from touching the table. For about half its whole length the upper part of the hull was flattened and formed a deck from which rose three short strong masts, each of which carried a wheel of thin metal whose spokes were six inclined fans something like the blades of a screw. A little lower than this deck there projected on each side a broad, oblong, slightly curved sheet of metal, very thin, but strengthened by means of wire braces, till it was as rigid as a plate of solid steel, although it only weighed a few ounces. These air-planes worked on an axis amidships, and could be inclined either way through an angle of thirty degrees. At the pointed stern there revolved a powerful four-bladed propeller, and from each quarter, inclined slightly outwards from the middle line of the vessel, projected a somewhat smaller screw working underneath the after end of the air-planes.