FUMAROLE  , a vent from which volcanic vapours issue, named indirectly from the

Lat. fumariolum, a smoke-hole . Fumaric acid . The vapours from fumaroles were studied first by R . W . Bunsen, on his visit to Iceland, and afterwards by H . Sainte-Claire Deville and other chemists and geologists in France, who examined the vapours from Santorin, Etna, &c . The hottest vapours issue from dry fumaroles, at temperatures of at least sod' C., and consist chiefly of anhydrous chlorides, notably sodium chloride . The acid fumaroles yield vapours of Tower temperature (3000 to 400°) containing much water vapour, with hydrogen chloride and sulphur dioxide . The alkaline fumaroles are still cooler, though above too°, and evolve ammonium chloride with other vapours . Cold fumaroles, below too°, discharge principally aqueous vapour, with carbon dioxide, and perhaps hydrogen sulphide . The fumaroles of Mont Pele in Martinique during the eruption of 1902 were examined by A . Lacroix, and the vapours analysed by H .

Moissan, who found that they consisted chiefly of water vapour, with hydrogen chloride, sulphur, carbon dioxide, carbon monoxide, methane, hydrogen, nitrogen, oxygen and argon . These vapours issued at a temperature of about 400° . Armand Gautier has pointed out that these gases are practically of the same composition as those which he obtained on heating granite and certain other rocks . (See VOLCANO) .