A minute chronometer, whose dial adorned the top exterior part of one of the curved arms, had the task of turning the lens at certain very definite times, by means of an artful connection between its movement and the contiguous pivot.

To ensure the stability of the whole structure, there was a horizontal rod ending in a globular counterpoise, like half a dumb bell, which was screwed into the side of the aluminium bar directly opposite the lens and the mirrors.

An enormous magnetic needle, seeming to belong to some gigantic compass, traversed the bar at right angles halfway up. Being the same length both sides, its magnetism served to hold the aerial device constant while in flight, in an unchangeable orientation. Its northern point was situated directly above the mirror looking south, whereas its southern spike coincided with the spherical counterpoise in the same way, though at closer range.

By way of a base there were three small aluminium claws which supported the bottom of the bar; they were quite smooth and curved, resembling miniature feet of a piece of furniture. Each rested its tip on the ground and supported the paving beetle firmly enough, while displaying, right at the bottom of its smoothly bulging curve, the dial of a minute chronometer hardly wider than itself. Halfway up each of the three claws, three thin horizontal nails were firmly fixed so as to converge inward. Their points sank very slightly into the rim of a blue metal disc, which was thus held flat and isolated in space exactly beneath the axis of the bar. A second disc, similar in shape but of light gray-colored metal, was positioned just above the other and about a millimeter away from it. It was suspended by a slender, vertical rod attached by one end to the center of its upper surface and vanishing into the bar. Just above the level of the claws’ attachment, the dial of a final chronometer was mounted at a peripheral point on the very bottom of the bar.

Having given us time to examine the punner thoroughly, Canterel retraced his steps, followed by our group, and a few moments later we had recrossed the cord and ranged ourselves along it in our original positions.

Soon our eyes were drawn toward the bottom of the apparatus by the sound of a slight impact: the gray disc, between the three claws, had been thrust down by its rod, quickly joining the other, and now both were pressed tightly together. At the precise moment when they touched the brown tooth lying beneath them left the ground and adhered to the back of the blue disc, obeying some mysterious magnetic attraction. To our ears the two collisions appeared simultaneous, making a single, united sound.

Shortly afterward a flash of light darted from the lens, which had abruptly made a quarter-turn by pivoting on the axis of its horizontal diameter and was now perpendicularly intersecting the oblique, descending path of the light-beam emitted by the mirror pointing south. As a result of this maneuver, the rays passed through the special glass and became powerfully concentrated on the whole area of the yellow substance spread out on the circular tray beneath the aerostat; a few of the delicate lower threads of the netting striped this suddenly glistening expanse with imperceptible shadows. As an effect of the intense heat thus generated, the ocher material must have released a light gas which entered the balloon through its bell-mouthed opening, for the envelope gradually began to swell. The upward force was soon great enough to lift the whole apparatus, which leapt gently into the air — while the lens made another quarter-turn in the same direction and darkened the yellow mixture by ceasing to concentrate the sun’s rays upon it.

While we were standing beyond the rope barrier the wind had changed and the punner was conveyed back to the picture made of teeth, but this second journey was made at a rather wide angle relative to the first and the instrument betook itself to the darkest corner of the crypt where the warrior was drowsing. During the flight the bottom of one of the claws was automatically lengthened by the lowering of an internal needle by half a centimeter.

Soon the balloon deflated appreciably, and as the apparatus de­scended it tackled with its two unextended claws a group of dark teeth belonging to one bank of the subterranean pool, while the needle that had just come into view was set down right upon the ground in the middle of an empty space. At the moment of touch-down, we saw the still-gaping valve on top of the aerostat soundlessly closed by its plug, after letting the required amount of gas escape. This plug was a plain aluminium disc capable of appearing or disappearing alternately as it revolved round a pivot attached to a point on its very edge, without changing its plane. Reasoning by analogy, we now understood how the paving beetle had performed its first journey by means of the lens and the valve, the respective operations of which had at that time escaped our inexperienced eyes.

The gray disc between the three claws had just been lifted again by its rod and a one-millimeter gap once more separated it from the blue one. Proving that the magnetic effect had been thereby destroyed, the nicotine-stained tooth, which had accompanied the apparatus through the air, at once quitted the back of the blue disc and fell to the ground, where it helped to fill in an unfinished part of the mosaic. The new arrival’s color harmonized with that of its neighbors, its tiny contribution in the right place making the picture slightly more complete.

The lens made a quarter-turn in the usual direction and the em­anations of the ocher substance, as the light warmed it, inflated the skin. The balloon rose, while the needle extension reentered the claw which performed the function of a sheath. Since the breeze had retained its latest direction, the punner pursued its course in a straight line to a slender, pointed pink root lying some distance away by itself, upon which an operation of the valve made it descend and come to rest.

∗ ∗ ∗

Then Canterel began to speak, explaining to us the purpose of the strange aerial vehicle.

The professor had developed the art of weather-forecasting to its furthest possible limits. Examination of a mass of fantastically sensitive and accurate instruments enabled him to determine the direction and force of every breath of wind at a given spot ten days in advance, as well as the time of arrival, dimensions, opacity and condensation potential of the smallest cloud.

In order to throw the extreme perfection of his forecasts into striking relief, Canterel conceived a device capable of creating a work of aesthetic merit solely due to the combined efforts of the sun and wind. He constructed the punner that stood before our eyes and provided it with five very accurate chronometers whose task was to regulate all its operations. The top one opened or shut the valve, while the others, working the mirrors and the lens, were employed in using the solar rays to inflate the aerostat’s envelope by means of the yellow substance. The latter, due to its special preparation, released a certain quantity of hydrogen whenever there was an increase in temperature. The ocher compound had been invented by the professor himself and its lightening exhalations were evolved only when the lens concentrated the sun’s burning rays upon it. In this way Canterel possessed an instrument which could make use of a particular air current foreseen long before to perform an accurate journey, with no other assistance than that of the more or less unobscured sun.

Then the professor looked round for a material to use in the begetting of his work of art. It seemed to him that only a fine mosaic could give rise to the frequent and captious flights of the apparatus to and fro. Now it was necessary that the multicolored pieces should be first attracted, then released by the lower part of the paving beetle, by some intermittent magnetism.