Pratt

John Henry Pratt

Born: 4 June 1809 in London, England
Died: 28 Dec 1871 in Ghazipur, India

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Pratt's main work was on the shape of the Earth. He gave 26.9 miles as the difference between the equatorial and polar axes, quite a good result. In 1855 he postulated density differences in the Earth's crust, lower densities under mountains, higher densities in lowlands, to explain the (too nearly constant) values obtained for gravity at a given latitude.

In the same year Airy offered a different explanation of the gravitational data. Both proposals have their merits but are oversimplifications of the actual situation.

Filled with missionary zeal, Pratt spent a large part of his life in the Church in Calcutta.

References:

  1. Dictionary of Scientific Biography 
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JOC/EFR February 1996