Founders of Seismology.—I. John Michell. 99 
result of that step. Ina smaller man such a life might have ended 
in stagnation, but, with his musical evenings at home, his friendship 
with many leading men of science, and his frequent visits to London, 
Michell maintained his freshness, and science rather gained than 
lost by the change. Happy in his social life, unfailing in the discharge 
of his parochial duties, and evidently possessing means sufficient for 
his wants, Michell carried on his scientific work without pause and 
without hurry, touching nothing that he did not adorn, and careless, 
apparently, to whom the credit might fall so long as the work was 
done. He died at Thornhill on April 21, 1793, in his 69th year.t 
Except for his early Treatise of Artificial Magnets and his memoir 
on earthquakes, Michell’s work was mainly astronomical. At the 
age of 25 he discovered the method of making magnets by 
double touch and the variation of magnetic action according 
to the inverse square of the distance. Less than ten years 
later he developed those clear views on stratification that are fully 
appreciated by modern geologists. Equally original and no less 
important was his memoir on stellar parallax (1767). In this he 
insisted on the extreme minuteness of the parallax of even the 
brightest stars, and inferred that the nearest fixed star is probably 
no farther from us than 220,000 times the sun’s distance—a quite 
close, if accidental, approximation to the distance ofa Centauri. The 
apparent proper motion of the stars he correctly attributed in part 
to that of the sun; he estimated the extreme probability that the 
stars which form the Pleiades constitute a connected system, and 
he foresaw the discovery, made shortly afterwards by Herschel, of 
the revolutions of the double stars. At Thornhill he experimented 
on the best alloys for the mirrors of reflecting telescopes and on 
the method of giving the mirrors their proper form. The 10 ft. 
reflector which he made was afterwards hought and used by 
William Herschel. Michell also invented the torsion-balance, 
and devised a method for determining the density of the earth. The 
apparatus was completed a short time before his death, but he did 
not live to make any experiment with it. It passed ultimately into 
the capable hands of Henry Cavendish, and led to his well-known 
determination of the density of the earth. Michell, like Darwin, 
was evidently one of those men who “seemed by gentle persuasion 
to have penetrated that reserve of nature which baffles smaller men’’. 
Is it too much to claim for him a place, not, indeed, beside Newton 
and Darwin, but in a rank not so very far below them ? 
During his own life Michell’s extraordinary power was known 
and valued. Among his friends he could number such men as 
Cavendish, Black, Priestley, and William Herschel. It is all the 
stranger, then, that his memoir on the cause and phenomena of 
1 The above biographical details are derived chiefly from articles in the 
Dictionary of National Biography; the English Mechanic, vol. xiii, 1871, 
pp. 309-10; Knowledge, vol. xv, 1892, pp. 188-91, 206-8; and Sir A. 
Geikie’s Memoir of John Michell (Camb. Univ. Press), 1918. 
