THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. II. 



No. I.— JANUARY, 1875. 



OIK-IO-IISJ-J^Xj aeticles. 



I. — Contributions to the Study of Volcanos. 

 By J. W. Judd, F.G.S. 



Introduction. 



n"!HE study of the nature and causes of the phenomena of volcanic 

 I activity, which for some time previously seemed to have almost 

 fallen into abeyance, has during the last few years attracted the 

 attention of many patient observers and earnest thinkers. In proof 

 of this statement, we need only point to the valuable essays upon 

 the subject which have recently been published by Dana, James 

 Hall, Le Conte, Shaler, Hilgard, Sterry Hunt, and others in America, 

 and to those by Mr. Mallet, Captain Hutton, the Eev. 0. Fisher, and 

 others in this country. 



But while we cannot but regard with pleasm-e the revival of 

 research in this important department of geological inquiry, it will 

 be well not to overlook a source of danger in the direction which it 

 seems to be almost exclusively taking. 



The earliest speculations on the subject of Yulcanology belong to 

 the domain of Cosmogony, rather than to that of Geology. With 

 the smallest basis of knowledge of the actual phenomena of volcanic 

 activity, theorists sought to build up " Systems of the Earth," in 

 which recourse was freely had to igneous action to accomplish all 

 such operations which were felt to be necessary for the removal of 

 the difficulties of their hypotheses. 



During the latter portion of the last century, however, the accurate 

 study of the phenomena presented by active volcanos was com- 

 menced by Sir William Hamilton, Dolomieu, and Spallanzani, in 

 that district of Europe where they are most admirably displayed, 

 namely, Southern Italy. A little later Hutton, with his able co- 

 adjutors and exponents, Sir James Hall, Playfair, and Macculloch, 

 sought to apply the phenomena of active volcanos to the explanation 

 of the appearances presented by those ancient rocks, in which the 

 signs of igenous action were clearly visible ; and in no country 

 could they have been more favourably situated for carrying on 

 such researches than in Scotland. 



In the two schools which we have thus noticed as taking their 

 rise at no distant date from one another, in Italy and Scotland re- 

 spectively, we have an indication of the two branches of inquiry into 

 which the study of Vulcanology must necessarily tend to flow. A 

 suggestive comparison may be draw between the investigation of 



DECADE II. — TOL. II. — NO. I. 1 



