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THE
International Scientific Series
VOL. XXXV.
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Frontispiece.
Sections of Igneous Rocks, illustrating the passage from theglassy to the crystalline structure.
1. Vitreous Rock. 2. Semi-Vitreous Rock. 3. Vitreous Rock withSphærulites. 4. Rock with Crypto-crystalline Base. 5. Rock withMicro-crystalline Base. 6. Rock of Granite Structure built upentirely of Crystals.
[See pp. 63-68.
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VOLCANOES
WHAT THEY ARE and WHAT THEY TEACH
BY
JOHN W. JUDD, F.R.S.
PROFESSOR OF GEOLOGY IN THE ROYAL SCHOOL OF MINES
WITH 96 ILLUSTRATIONS
SIXTH EDITION
LONDON
KEGAN PAUL, TRENCH, TRÜBNER & CO. Ltd.
PATERNOSTER HOUSE, CHARING CROSS ROAD
1903
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(The rights of translation and of reproduction are reserved.)
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PREFACE.
In preparing this work, I have aimed at carrying outa design suggested to me by the late Mr. PoulettScrope, the accomplishment of which has been unfortunatelydelayed, longer than I could have wished,by many pressing duties.
Mr. Scrope's well-known works, 'Volcanoes' and'The Geology and Extinct Volcanoes of Central France'—whichpassed through several editions in this country,and have been translated into the principalEuropean languages—embody the results of muchcareful observation and acute reasoning upon thequestions which the author made the study of his life.In the first of these works the phenomena of volcanicactivity are described, and its causes discussed; in thesecond it is shown that much insight concerning theseproblems may be obtained by a study of the ruined anddenuded relics of the volcanoes of former geologicalperiods. The appearance of these works, in the years- viii -1825 and 1827 respectively, did much to prepare theminds of the earlier cultivators of science for thereception of those doctrines of geological uniformityand continuity, which were shortly afterwards so ablyadvocated by Lyell in his 'Principles of Geology.'
Since the date of the appearance of the last editionsof Scrope's works, inquiry and speculation concerningthe nature and origin of volcanoes have been alikeactive, and many of the problems which were discussedby him, now present themselves under aspects entirelynew and different from those in which he was accusto