Rumblings in the air: understanding earthquakes in the 1690s.

After a wave of earthquakes in 1692 and 1693, the astronomer John Flamsteed composed an innovative explanation of their causes. He argued that they did not originate underground but were caused by explosions of nitrous and sulphurous particles in the air. Although the idea now sounds strange, Flamsteed's account was expressed in terms that were familiar to his contemporaries in the Royal Society, drawing particularly on Boyle's chemistry and air-pressure experiments. Flamsteed was more unusual in his conviction that the earth was virtually solid; this made him an opponent of structural theories offered by Thomas Burnet, Robert Hooke and Edmond Halley. Flamsteed's ideas were dismissed by Hooke as 'nonsensicall', but by the time they were published, long after his death, they appeared closer to mainstream thinking.