The daylight had become much more intense in the minutes Daniel had been up here. He saw that Hooke had rigged an articulated rod to the back of the piston, and connected the rod to a system of cranks. Now, by means of a tiny touch-hole in the base of the cylinder, he introduced fire to the chamber. Thump. The piston snapped up to the top of the bore much faster than Daniel could flinch away from it. This caused an instant of violent motion in the gear-train, which had the effect of winding a spring that spiraled around in a whirling hoop the size of a dinner-plate. A ratchet stopped this from unwinding. Hooke then re-arranged the gears so that the giant watch-spring was connected, by a string wound around a tapered drum, to the drive-shaft of a peculiar helical object, very light-weight, made of parchment stretched on a frame of steam-bent cane. Like a Screw of Archimedes. The spring unwound slowly, spinning the screw swiftly and steadily. Standing at one end of it, Daniel felt a palpable breeze, which continued for more than a minute – Hooke timed it with his latest watch.