314 



THE GEOLOGIST. 



Lathyrus Aphaca and Lathyrus Nissolia have been very abundant tbis year 

 on the' Keiiper sandstones and marls, but Mr. Symonds has not seen a single 

 specimen of the former plant upon the adjoining Lias of the district. Carex 

 montana grows only on carboniferous limestone. The rarer plants of Snowdon 

 appear to have selected bands of volcanic tuff, intermingled with calcareous 

 deposits for their habitat. Mr. Symonds particularly asked for the attention 

 of geologists to the Tlora of insulated trap rocks. 



ON THE COEEUGATION OF STRATA IN THE VICINITY OF 

 MOUNTAIN EANGES. 



By the Rev. J. Dingle. 



This paper was in continuation of some former papers which had been read 

 before the Association, in which an attempt had been made to determine the 

 mode of the formation and development of the earth's crust, from physical, 

 geographical, and geological considerations. The author described the varying 

 forms of flexure, diminishing in intensity with their distance from the igneous 

 axis, which characterizes the strata in the neighbourhood of the mountain 

 chains, and showed how this form would arise from the action of the molten 

 interior of the earth near the fissures in the crust. The fluid lava rising in a 

 fissure must have reacted on the general mass beneath, and caused an upward 

 pressure on the crust on each side. Now it has been proved by experiment in 

 the case of a column of fluid, that, in the propagation of the condensation 

 produced by the weight of the column, there were points of maximum and 

 minimum pressure along the surface of the fluid from which the column arose ; 

 and hence in the case of the fissures we might generally expect successive cor- 

 rugations, subsequently lifted up, and sometimes falling over at last into one 

 dip, just as we actually find them. The author expressed his obligations to 

 Professor H. D. Rogers for the valuable information w^hich he had derived 

 from an important paper of his on the subject in the Transactions of the Royal 

 Society of Edinburgh for 1857, but demurred to some of his hypotheses. 

 Mexures at definite points in solid strata must be produced by repeated and 

 continued fissures, and not by paroxysmal action. The latter chiefly spends 

 itself in earthquakes and volcanos, which, upon the whole, can produce no con- 

 tinuous change of form. The two kinds of forces appear, however, to be inti- 

 mately related to each other ; and if we suppose the one to be only tlie other 

 in excess, we are supplied with a simple explanation of the connection between 

 the corrugated mountain chains, and the lines of earthquakes and volcanos. 



As a corollary from the above views, it might be observed that they destroyed 

 tJie idea of any distinct theory of volcanos. whether of elevation or eruption ; 

 for the quantities of elevated* and ejected matter in the case of a fissure or a 

 ru])turcd corrugation might be in all possible proportions to each other. 



The author expressed his confidence that in this and his former papers he had 

 pointed out tlie true means of determining the mode of formation of the 

 earth's crust from the consideration of existing facts and well-kno\^Ti physical 

 laws— a branch of geological science in which nothing had been done Ijefore 

 beyond starting a few crude and ill-supported guesses. 



A brief conversation followed the reading of the paper, in which Professor 

 Rogers expressed his general acquiescence with the author's views on some 

 important points connected with the formation of the earth's crust, 



