French naval
commander. He fought in the Antilles (1680) and in Abraham Duquesne's
Algerian campaign (1682-83) and from 1685 to 1687 was grand admiral
and generalissimo of the king of Siam. Forbin distinguished himself
in the War of the Grand Alliance and the War of the Spanish Succession.
He failed (1708) in an attempt to land James Francis Edward Stuart,
the Old Pretender, in Scotland. His memoirs were published in
1729?30.
reflections
in rhombs of rock-salt. His work won him the Rumford medal of
the Royal Society in 1838, and in 1843 he received its Royal medal
for a paper on the” Transparency of the Atmosphere and the Laws
of Extinction of the Sun’s Rays passing through it.” In 1846 he
began experiments on the temperature of the earth at different
depths and in different soils near Edinburgh, which yielded determinations
of the thermal conductivity of trap-tufa, sandstone and pure loose
sand. Towards the end of his life he was occupied with experimental
inquiries into the laws of the conduction of heat in bars, and
his last piece of work was to show that the thermal conductivity
of iron diminishes with increase of temperature. His attention
was directed to the question of the flow of glaciers in 1840 when
he met Louis Agassiz at the Glasgow meeting of the British Association,
and in subsequent years he made several visits to Switzerland
and also to Norway for the purpose of obtaining accurate data.
His observations led him to the view that a glacier is an imperfect
fluid or a viscous body which is urged down slopes of a certain
inclination by the mutual pressure of its parts, and involved
him in some controversy with Tyndali and others both as to priority
and to scientific principle. Forbes was also interested in geology,
and published memoirs on the thermal springs of the Pyrenees,
on the extinct volcanoes of the Vivarais (Ardeche), on the geology
of the Cuchullin and Eildon hills, &c. In addition to about
i5o scientific papers, he wrote Travels through the Alps of Savoy
and Other Parts of the Pennine Chain, with Observations on the
Phenomena of Glaciers (1843); Norway and its Glaciers (1853);
Occasiona~l Papers on tile Theory of Glaciers (1859); A Tour of
Mont Blanc and Monte Rosa (1855). He was also the author (I852)
of the “Dissertation on the Progress of Mathematical and Physical
Science,” published in the 8th edition of the Encyclopaedia Britannica.
See Forbes’s Life and LeUers, by Principal Shairp, Professor P.
G. Tait and A. Adams-Reilly (1873); Professor Forbes and his Biographers,
by J. Tyndall (1873).
Illustrated by RN.
