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Some Thoughts of Erasmus Darwin


knocker
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  • Location: Camborne
  • Location: Camborne

    Led by the larger than life Erasmus Darwin, the Lunar Society of Birmingham were a group of eighteen century amateur esperimenters who met monthly on the Monday night nearest to the full moon. But sticking with Darwin.

     

    Working with Watt, Priestley and Joseph Black on properties of water Darwin added some imaginative speculations, working out - for the first time - how air cools when it expands, and applying this to explain how clouds form when air rises and expands in the less pressurized higher reaches of the atmosphere, cooling and condensing in the process.

     

    This courtesy of Jenny Uglow.

     

     

    In the years ahead Darwin would become increasingly absorbed by meteorology. From the late 1770s, all over Europe, ideas about the link between climate and health had encouraged organized observation. And Darwin's practice, which took him out in all weathers, inspired ingenious devices, such as a weather-forecasting device - a pointer on his study ceiling, connected to a weather-vane above (probably made by Whitehurst), which showed him the direction if not the force of the wind. He was becoming  more and more interested in the winds themselves: in the sudden change from cold to warm as a south-west breeze replaced a northerly; in the formation of clouds and the patterns of weather. While his pointer showed the sudden changes, another instrunlent, an open tube attached to a chinmey, with a windmill sail and a series of cogged wheels to show the revolutions, let him meter the north-south airflow. Soon he would develop his own theories of the global movement of the winds, making a series of significant discoveries, including the identification of warm and cold fronts, not rediscovered until the 1920s. His language and imagery remained that of his day, although his thoughts raced ahead. The air was 'rarified', he thought, on a line south of the British Isles, '& rises in a heap, which moulders down on the lower parts of the atmosphere, like the sand in an hour glass'. A current flowed from the cold Poles to the Equator, until the 'heap' at the line was heavier than the polar air,'& then the air oscillates, being very elastic & the upper part having no friction, like a pendulum'.  The movement from west to east, as opposed to north and south, he thought, was a function of the movement of the earth itself:eddies in the great air mass swirled and crashed, monsoons were born, trade winds arose, zephyrs played and thunder roared.

     

    This group of men came up with an extraordinary number of ideas and inventions.

     

    Source.

    Jenny Uglow, The Lunar Men, Faber and Faber, 2002.

    Edited by knocker
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