EDWARD HULL, M.A., LL.D., F.R.S.
Examiner in Geology to the University of London.
WITH 41 ILLUSTRATIONS AND 4 PLATES OF ROCK-SECTIONS.
LONDON:
WALTER SCOTT, Limited,
24, WARWICK LANE, PATERNOSTER ROW.
1892.
By THE SAME AUTHOR.
The Coal-fields of Great Britain: their History, Structure, and Resources. 4th edit. (1881.) E. Stanford.
The Physical History of the British Isles. With a Dissertation on the Origin of Western Europe and of the Atlantic Ocean. (1882.) E. Stanford.
The Physical Geology and Geography of Ireland. 2nd edit. (1891.) E. Stanford.
Treatise on the Building and Ornamental Stones of Great Britain and Foreign Countries. (1872.) Macmillan and Co.
Memoir on the Physical Geology and Geography of Arabia-Petræa, Palestine, and adjoining Districts. (1886.) Committee of the Palestine Exploration Fund.
Mount Seir, Sinai, and Western Palestine. Being a Narrative of a Scientific Expedition, 1883-84. (1885.) Committee of the Palestine Exploration Fund.
Text-book of Physiography. (1888.) C. W. Deacon and Co.
Sketch of Geological History. (1887.) C. W. Deacon and Co.
PREFACE.
It has not been my object to present in the following pages even an approximately complete description of the volcanic and seismic phenomena of the globe; such an undertaking would involve an amount of labour which few would be bold enough to attempt; nor would it be compatible with the aims of the Contemporary Science Series.
I have rather chosen to illustrate the most recent conclusions regarding the phenomena and origin of volcanic action, by the selection of examples drawn from the districts where these phenomena have been most carefully observed and recorded under the light of modern geological science. I have also endeavoured to show, by illustrations carried back into later geological epochs, how the volcanic phenomena of the present day do not differ in kind, though they may in degree, from those of the past history of our globe. For not only do the modes of eruption of volcanic materials in past geological times resemble those of the present or human epoch, but the materials themselves are so similar in character that it is only in consequence of alterations in structure or composition which the original materials have undergone, since their extrusion, that any important distinctions can be recognised between the volcanic products of recent times and those of earlier periods.
I have, finally, endeavoured to find an answer to two interesting and important questions: (1) Are we now living in an epoch of extraordinary volcanic energy?—a question which such terrible outbursts as we have recently witnessed in Japan, the Malay Archipelago, and even in Italy, naturally suggest; and (2) What is the ultimate cause of volcanic action? On this latter point I am gratified to find that my conclusions are in accordance with those expounded by one who has been appropriately designated "the Nestor of Modern Geology," Professor Prestwich.
Within the last few years the study of the structure and composition of volcanic rocks, by means of the microscope brought to bear on their translucent sections, has added wonderfully to our knowledge of such rocks, and has become a special branch of petrological investigation. Commenced by Sorby, and carried on by Allport, Zirkel, Rosenbusch, Von Lasaulx, Teall, and many more enthusiastic students, it has thrown a flood of light upon our knowledge of the mutual relations of the component minerals of igneous masses, the alteration these minerals have undergone in some cases, and the conditions under which they have been erupted and consolidated. But nothing that has been observed has tended materially to alter conclusions arrived at by other processes of reasoning regarding volcanic phenomena, and for these we have to fall back upon observations conducted in the field on a more or less large scale, and carried on before, during, and after eruptions. Macroscopic and microscopic observations have to go hand in hand in the study of volcanic phenomena.
E. H.