Autograph letter signed to Robert Were Fox.
Saint Véran, Avignon Nov 23, 1866
Octavo, 16.8 x 10.9 cm, 4 pages in ink, with the original envelope and stamp and stamped Avignon 23 Nov and on the back Hyeres 25 Nov, the back of the envelope embossed JSM.
Robert Were Fox [1789-1877] of the wealthy and cultivated family of Quakers of Falmouth in Cornwall. In 1814, during his wedding trip on the continent, he formed lasting friendships with F W H A von Humboldt and other foreign scientists. His researches began in 1812 with Joel Lean, when they performed a series of experiments hoping to improve Watt's engines which were used in Cornish mines. In 1815 Fox began his researches into the internal temperature of the earth, which continued throughout his life. Facilities were provided for this by his lifelong connection with Cornish mines. Fox was the first to prove definitively that heat increased with depth, and that this increase was in diminishing ratio as depth increased. Fox was also interested in magnetic phenomena, especially relating to the earth's magnetism, and constructed a new dipping needle of great sensitivity and accuracy which was later used by Sir James Clark Ross in his voyage to the Antarctic in 1837 and by Captain Nares in the expedition to the North Pole in 1875-1877. Fox was one of the founders of the Royal Cornwall Polytechnic Society in 1833, and was Vice President several times. Mill must have first met him when in March 1840 he went to Falmouth where his brother Henry had been taken ill on his way to Madeira and cared for by the Fox family.
Mineka, The Later Letters of John Stuart Mill, no.1009