GLIDE, SAIL, SOAR

A northeast wind is picking up. Two redtail hawks are circling above this ridge, rising higher and higher, sliding fast when they turn southward but seeming to hover in place when they face north. Each surge and billow lifts them higher. They must soar for pleasure; they're so far up now, no likely prey would hold still long enough for them to stoop to seize it

- PETER GARRISON

A HUNDRED AND TWENTY YEARS AGO, people were arguing about how they did it. They watched buzzards glide from horizon to horizon without moving their wings, and guessed they must be harvesting some mysterious essence of upness from the air. Few seemed to realise that air moves up and down as well as horizontally. One who did was Hiram Maxim, an expatriate American living in England who invented, among other things, a most efficient piece of harvesting equipment, the machine gun.

Maxim was, among many other things, a serious aeronautical experimenter who built a huge aeroplane that might have flown – albeit uncontrollably – had it not been prudently secured to the ground by tracks both above and below its wheels. With a thorough understanding of physical laws and a keen eye for the sea and the sky and the birds in between, Maxim correctly analysed the dynamics of bird flight. One of his papers, entitled “Natural and Artificial Flight”, can be found in an edition of the Aeronautical Annual for 1896. These Annuals – three of them -- were compilations of writing and thinking on human flight, mostly contemporary, but some dating back as far as Leonardo, which appeared from 1895 to 1897. They are available in modern reprints from aeronauticalpublishers.com and give fascinating insights into the now muddled, now lucid state of aeronautical thinking in the years just before powered flight was finally achieved.