1869.] HUNT — ON VOLCANOES AND EARTHQUAKES. 397 



the period of depression of the area of sedimentation, il we may 

 judge from the energy and copiousness of the eruptions of island 

 volcanoes, although the activity is still prolonged afier the period 

 of elevation. 



As regards the geological importance of volcanic and earthquake 

 phenomena, their significance is but local and accidental. 

 Volcanoes and earthquakes are and always have been confined to 

 limited areas of the earth's surface, and the products of volcanic 

 action make up but a small portion of the solid ciust of the globe. 

 Great mountains and mountain chains are not volcanic in their 

 nature or their origin, though sometimes crowned by volcanic 

 cones ; nor are earthquakes and volcanoes to be looked upon as 

 anything more than incidental attendants upon the great agencies 

 wnich are slowly but constantly raising and depressing continents. 



The theory of volcanic phenomena here set forth was first 

 partially indicated by Keferstein in 1834<, and subsequently and 

 apparently independently by Sir John Herschel in 1837. It, 

 however, attracted little or no attention until, in 1858 and 1859, 

 I again brought it forward, and endeavoured to show its 

 conformity with the facts of chemistry, physics, and geognosy. 

 In the hasty sketch of it here given, the chemist, the geologist, 

 and the geographer will alike discover points which require 

 elucidation or provoke criticism, but will, I hope, find, 

 nevertheless, a concise and intelligible statement of a theory of 

 earthquakes and volcanoes which appears to me more in harmony 

 with the known facts of science than any other hitherto advanced. 



P. S. — In justice to myself, it should be said that at the time this 

 lecture was delivered I had no knowledge of Prof. J. D. Whitney's 

 excellent and suggestive paper on earthqualjes, which appears in The 

 North America)i Eevieio for April, 1869. The relation of modern 

 volcanic phenomena to great accumulations of newer secondary and 

 tertiary rocks, and the conneoticm of the foldings and contortions of 

 sedimentary strata with great thicknesses of the same, are set forth by 

 me in several papers, the chief of which may be found in the Canadian 

 Journal for May, 1858, the Geological Journal for JSTovember, 185&, and 

 the American Journal of Science for July, 186U (vol. xxx., p. 133), and 

 also for May, 1861 (vol. xxxi., pages 406-414), where the important 

 contributions of Professor James Hall, bearing upon this question, are 

 noticed at length. 



