INOKGANIC GEOLOGICAL DYNAMICS. 557 



and elevating them in a conical form. Against this doctrine, as exem- 

 plified in the most noted instances, strong arguments have been adduced 

 by other geologists. Yet the protrusion of fused rock by subterrana- 

 ous forces upon a large scale is not denied : and how far the examples 

 of such operations may, in any cases, be termed craters of elevation, 

 must be considered as a question not yet decided. On the supposition 

 of the truth of Von Buch's doctrine, M. de Beaumont has calculated 

 the relations of position, the fissures, &c., which would arise. And 

 Mr. Hopkins, 9 of Cambridge, has investigated in a much more general 

 manner, upon mechanical principles, the laws of the elevations, fissures, 

 faults, veins, and other phenomena which would result from an eleva- 

 tory force, acting simultaneously at every point beneath extensive por- 

 tions of the crust of the earth. An application of mathematical rea- 

 soning to the illustration of the phenomena of veins had before been 

 made in Germany by Schmidt and Zimmerman. 10 The conclusion 

 which Mr. Hopkins has obtained, respecting the two sets of fissures, at 

 right angles to each other, which would in general be produced by 

 such forces as he supposes, may suggest interesting points of examina- 

 tion respecting the geological phenomena of fissured districts. 



[2nd Ed.] [The theory of craters of elevation probably errs rather 

 by making the elevation of a point into a particular class of volcanic 

 agency, than by giving volcanic agency too great a power of elevation. 



A mature consideration of the subject will make us hesitate to 

 ascribe much value to the labors of those writers who have applied 

 mathematical reasoning to geological questions. Such reasoning, when 

 it is carried to the extent which requires symbolical processes, has 

 always been, I conceive, a source, not of knowledge, but of error, and 

 confusion ; for in such applications the real questions are slurred over 

 in the hypothetical assumptions of the mathematician, while the calcu- 

 lation misleads its followers by a false aspect of demonstration. All 

 symbolical reasonings concerning the fissures of a semi-rigid mass pro- 

 duced by elevatory or other forces, appear to me to have turned out 

 valueless. At the same time it cannot be too strongly borne in mind, 

 that mathematical and mechanical habits of thought are requisite to 

 all clear thinking on such subjects.] 



Other forces, still more secure in their nature and laws, have played 

 a. very important part in the formation of the earth's crust. I speak 

 of the forces by which the crystalline, slaty, and jointed structure of 



9 T, ins. Camb. Phil. Soc. vol. vi. 1836. lo Phil. Mac,. July, 1836, p. 2 



