# Dictionary of National Biography, 1885-1900/Hadley, George (1685-1768)

​HADLEY, GEORGE (1685–1768), scientific writer, born in London on 12 Feb. 1685, was a younger brother of John Hadley (1682–1744) [q. v.], who invented the reflecting quadrant. George entered Pembroke College, Oxford, 30 May 1700, and on 13 Aug. 1701 became a member of Lincoln's Inn. He was called to the bar 1 July 1709, but appears to have been more occupied with mechanical and physical studies than in professional work. An anonymous pamphlet in the British Museum which describes the quadrant was written by him, according to a manuscript note on the margin, and he is most probably the author of a Latin version of the same tract which has been bound up with it.
His main claim to notice is that he first clearly formulated the present theory of trade winds. Galileo, Halley, and Hooke had discussed air-currents, and the two latter had attributed them to the rarefying power of the sun's heat, but Hadley was the first who adequately studied the direction of these currents. Being elected a fellow of the Royal Society 20 Feb. 1735, it was on 22 May of the same year that he presented his paper 'Concerning the Cause of the General Trade Winds' (Phil. Trans. xxxix. 58) . After showing how the earth's diurnal rotation must be considered in explaining the trade winds, Hadley clearly sets forth first, the motion of the lower atmosphere from north and south towards the equator, with the causes of this motion; secondly, how the air 'as it moves from the tropicks towards the æquator, having a less velocity' of diurnal rotation 'than the parts of the earth it arrives at, will have a relative motion contrary to that of the earth in those parts, which being combined with the motion towards the aequator, a N.E. wind will be produced on this side of the æquator, and a S.E. on the other.'
This simple statement exactly represents the theory of the trade winds as still held by physicists, yet in Hadley's time and for sixty years after the date of his paper the truth and value of his explanation were unacknowledged. In 1793 Dalton, referring to one of his essays, says: 'The theory of the trade winds was, as I conceived when it was printed off, original; but I find since that they are explained on the very same principles and in the same manner by George Hadley, F.R.S.' (Meteorolog. Observations, &c. preface).
Hadley was for at least seven years in charge of the meteorological observations presented to the Royal Society, and drew up an 'Account and Abstract of the Meteorological Diaries communicated for the years 1729 and 1730.' On 9 Dec. 1742 he communicated a similar paper on the meteorology of 1731-5. After leaving London, he for some time lived with a nephew at East Barnet, but most of his later years were spent at Flitton in Bedfordshire, where his nephew, Hadley Cox, was vicar. Hadley died at Flitton on 28 June 1768. The vicar, who died in 1782, speaks affectionately of him in his will, and bequeaths to his son 'my reflecting telescope ​upon the condition that he never part with it, being the first of the sort that ever was made, invented by my late uncle, John Hadley, Esq., and made under the direction and with the assistance of his two brothers, George and Henry.'
R. E. A.