10 Sir Charles Lyett and Modern Otology. [Jul, 



great valoe of the service to science which Sir Charles Lyell per- 

 formed when he proposed it. 



Closely connected with the general subject of existing causes, 

 and forming a very important branch of the inquiry, are the 

 phenomena connected with volcanic eruptions and the formation of 

 cones and craters. Sir Charles Lyell has always taken a prominent 

 part in the discussions which have from time to time arisen re- 

 specting certain of these phenomena, and more especially in the 

 controversy between the partisans of iAm " crater of elevation n and 

 ~ crater of eruption " theories. The old theory of the formation of 

 volcanic cones was that a vent having been produced by the fracture 

 of the earth's crust (which may have been attended with some 

 degree of upheaval and dislocation), the volcanic materials sub- 

 sequently ejected gradually formed a conical mound, having a 

 depression in the centre. This mound, or "volcanic cone 

 supposed to be composed chiefly of ashes and scoria?, which have 

 been ejected into the air, and on felting have naturally arranged 

 themselves in the ™nnw stated. The eruption of dykes and 

 ; ;:-^^ ;: =.:lii '.:..~\ ir:i_ :"_t z.^~'.~ ::rr_r:: ::>:-: :.-->:- iz. n - .::^ 

 solidity to the cone, although it frequently destroys its symr 

 by breaking down the walls of one side of the crater. This -: 

 planation has been termed the " crater of eruption " theory, and is 

 the one which was most generally received until the celebrated 

 Leopold von Buch propounded the opposing theory of " craters of 

 e*.r-ir.:i.." £c ii-s. ~'zi:'z. — is -\-i :p-i :~ Hizioili:. ii: :i_Tie:*:-re 

 became generally received. Sir Charles Lyell and Mr. Pouflett 

 Serope have always been consistent in their opposition to it ; and 

 it is, perhaps, entirely owing to their united exertions that it has 

 n:~ i:-,L--=z- >: ii";i. — :•: nsr-riite. 



The "crater of elevation n theory may be thus stated : — A vent 

 having been formed in the earths crust, volcanic materials — lava, 

 ashes, and scoriae — are ejected and spread horizontally over the 

 surface, the cone being subsequently formed by sudden inflation 

 and upheaval from beneath. 



Sir Charles Lyell devotes several pages in the 'Principles 1 

 to the refutation of this theory, and it may be as well to enumerate 

 the chief points of his argument. In the first place, although 

 upheaved strata of various ages occur all over the world, no single 

 instance can be pointed out in which the upheaval has produced a 

 form comparable to that of a truncated volcanic cone. Sir Charles 

 Lyell therefore asks, "Are we then called upon to believe that 

 "i-Tir _ rr elisr!:- zi:I- i-fn-rrs.:*- — :ir iri: tendril, r-rii-::^ :."irs: 

 through horizontal strata, so as to upheave them in the peculiar 

 manner before adverted to, they always select, as if from choice, 

 those spots of comparatively insignificant area where a certain 

 quantity of volcanic matter happens to Be, while they carefully 



