The dead pigeons should have been James Glaisher’s warning. On 5 September 1862, the scientist was taking one of his first balloon flights – and alongside the compass, thermometers and bottles of brandy, he had decided to bring along six birds.

“One was thrown out at the height of three miles,” he later wrote. “When it extended its wings it dropped like a piece of paper; the second, at four miles, flew vigorously round and round, apparently taking a dip each time; a third was thrown out between four and five miles, and it fell downwards as a stone.”

No sooner had he noted these observations than he began to feel the “balloon sickness” himself. His arm had been resting on the table, but it failed to respond when he tried to lift it. Alarmed, he tried to call out to his aeronaut, Henry Coxwell, but the words froze in his mouth and his head lolled helplessly to one side.

Glaisher knew the end was nigh. “In an instance darkness overcame me… I believed I would experience nothing more as death would come unless we speedily descended.”

Amazingly, both Coxwell and Glaisher survived thanks to some last-minute luck – but had they not they would have drifted to their deaths at the edge of the Earth’s atmosphere. Their plight is one of the great daredevil stories in the history of aviation – and perhaps even a glimpse into the future of space travel.

The aerial ocean

Glaisher had first set his sights skyward as he surveyed Ireland, mapping the contours of its highest peaks. “I was often compelled to remain sometimes for long periods, above or enveloped in cloud,” he wrote. “I was thus led to study the colours of the sky, the delicate tints of the clouds, the motion of opaque masses, the forms of the crystals of snow.” His interest only peaked as he moved to the great observatories of Cambridge and Greenwich. “Often when a barrier of cloud has suddenly concealed the stars from view, I have wished to know the cause of their rapid formation and the processes in action around them.”