J. W. Jit dd — On Volcanos. 3 



in which the speculative portions are omitted. In the latter he has 

 confined his researches within the true limits of geological inquiry, 

 and the work remains the most complete and masterly treatise on 

 the subject which has yet been produced. 



In the " Principles of Geology " due weight has been assigned by 

 Sir Charles Lyell to igneous action in producing the existing features 

 of the globe. In order to illustrate the manner in which the 

 phenomena presented by the rocks of the globe are capable of 

 explanation by the operations now taking place on its surface, both 

 the "physiological" and "anatomical" branches of the subject are 

 treated with that force of argument, that justice of illustration, and that 

 felicity of language, with which every geologist is familiar. Mr. Dar- 

 win's works on South America and the Volcanic Islands of the Atlantic 

 may be regarded as additional and very valuable illustrations of the 

 "Principles of Geology," the work which, as he has himself assured 

 us, first led him into those lines of research in which he subsequently 

 attained such preeminent success. 



During the last fifty years innumerable very valuable contributions 

 to both branches of the science of Vulcanology have been made. 

 Geographers and travellers, physicists and chemists, mineralogists 

 and penologists, have accumulated the most valuable details, illustrat- 

 ing the nature and distribution, the characters and materials, the 

 phenomena and products of active volcanos. Humboldt, von Buch, 

 Hoffmann, Junghuhn, and others have occupied themselves with their 

 general features ; Gustave Eose, Abich, Scacchi, vom Path, and 

 Fuchs, with the rocks of which they are composed ; and Daubeny, 

 Deville, Fouque, and Janssen, with the chemical operations taking 

 place within them. 



Equally valuable have been the labours of those physical geologists 

 who have supplied us with detailed descriptions and accurate maps, 

 illustrating the features presented by the older igneous rock-masses and 

 their relations to the stratified deposits with which they are associated. 

 Foremost in this category we must mention Charles Maclaren, who 

 at so early a date described with admirable clearness the volcanic 

 rocks in the neighbourhood of Edinburgh, The maps and memoirs 

 of the Geological Survey, especially those relating to North Wales 

 and Central Scotland, also afford very valuable illustrations of the 

 older volcanic rocks. 



In some of the latest researches on Vulcanology, to which I have 

 referred at the commencement of this article, however, a tendency is 

 shown towards abandoning these safer methods of inquiry, based on 

 the doctrine of Uniformity, and reverting to the earlier methods — in 

 effect, to the substitution of Cosmogony for Geology. In the ingenious 

 theory elaborated by Mr. Mallet a still bolder course is adopted, and, 

 almost entirely ignoring the results of geological inquiry, this author 

 endeavours to build up on the foundation of the nebular hypothesis of 

 Laplace, and by the aid of those laws of Physics which he regards as 

 fully established, a system of " Vulcanicity." Had the Physical 

 Sciences attained their final stage of development, Mr. Mallet might 

 perhaps have been justified in taking such high ground as he does 



