Mary Reed

Weather Talk: Playing in the Wind

lthough very little is known about the ancient Greek mathA ematician, Hero, his legacy lives on today in books and musical instruments. In 185 1, Bennet Woodcroft, professor of machinery (engineering) at London’s University College, published a translation of Hero’s The Pneumatics of Hero ofillexander. It’s a pity not more is known about Hero, as his Pneumatics is a wonderful book, explaining how to construct devices that are intended to charm and entertain onlookers while at the same time puzzling them as to how they worked. One example included a pair of temple doors that opened unaided when an altar fire was lundled. Hero’s inventions were powered by compressed air, water, or steam. What caught my weather eye was what he described as an “altar organ blown by the agency of a windmill.” His design is deceptively simple. Music is played via an arrangement of wind-powered rods and pistons. As a set of small windmills rotates atop a post, they turn a horizontal rod whose end is attached to a circular plate edged with pegs. The rotating pegs intermittently strike another horizontal rod, which in turn raises a piston. When the striking peg has passed, the piston returns to its down position, thus forcing air out of the box into which it sinks. The air passes through a small tube leading back into the organ. Thus, the instrument plays on its own, apparently unaided by human hands. Since, of course, breezes gust in fits and starts, Hero helpfully added that the windmill post can be turned “towards the prevailing wind, that the revolution may be more rapid and uniform,” thus proHero’s ”altar organ” used wind power to make music.