John Henry Pratt

John Henry Pratt ( born June 4, 1809 in London, † December 28, 1871 in Ghazipur, India) was an English cleric and mathematician. He designed a theory of the equilibrium of the earth's crust, which was one of the cornerstones of the theory of isostasy, and correctly recognized that the Earth is flattened at the poles. His provision of this flattening as the difference of the axes by pole and equator corresponded almost the currently known value at 26.9 miles ( 43.3 kilometers ).

Life

Pratt was born the son of Elizabeth Jowett and Josiah Pratt, a vicar of the Church of England. He attended Oakham School in Rutland before 1829 at Gonville and Caius College, University of Cambridge enrolled, from which he graduated in 1833 with a Bachelor of Arts. In 1836 he took off his master at Christ 's and Sidney Sussex College. Under the influence of his father, he embarked on a clerical career and in 1838 chaplain to the East India Company. Six years later he moved to Daniel Wilson, the then Bishop of Calcutta, and six years later he was in 1850 Archdeacon of Calcutta. In 1871, he died during a visit to Ghazipur in Uttar Pradesh of cholera.

Work

His first work was The Mathematical Principles of Mechanical Philosophy and Their application to Elementary Mechanics and Architecture, but chiefly to the Theory of Universal Gravitation, the work of more than 600 pages, published in 1836 in the first edition and first under the short title Pratt 's Mechanical Philosophy became known. 1842 appeared the second edition, and after a thorough revision of 1860, the third, this time under the title On attractions, Laplace 's functions and the figure of the Earth. In addition to his scientific work, Pratt published several theological works, his 1856 published book Scripture and science not at variance tried science and faith to reconcile and was repeatedly reprinted.

His theory of the equilibrium of the earth's crust, he developed on the basis of surveying the land that George Everest had done. When the results of the trigonometric measurement of the longest distance between the northernmost and southernmost point of India were compared with that from astronomical, there is a small difference between these figures showed. Everest explained this difference with measurement errors, but Pratt investigated the cause is that the mass of the Himalayas distracted the lead solder used in the survey. As he pursued this theory, he discovered that the deflection of the lots could not have been as great as he had calculated from the density and volume of the mountains: the difference between the trigonometric and astronomical length determination would have to be greater than observed. As an explanation, he assumed that the density of the Earth's crust in the Himalayas is lower than in the plane. His theory was published in the same year as the second theory of isostasy, the George Biddell Airy had developed.

1866 Pratt was appointed a Fellow of the Royal Society.