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VII. — Experimental Researches in Mountain Building. By Henry M. Cadell 

 of Grange, B.Sc, F.E.S.E., H.M. Geological Survey of Scotland. 



(Read 20th February 1888.) 



PART I. 



A. On the Behaviour of Strata when thrust over an Immovable Surface. 



B. On the Origin of Thrust-Planes and " Fan Structure." 



C. On the Relation between Folding and Regional Metamorphism. 



D. General Summary of Results. 



Introduction. 



Among most of the geologists who had of late years been engaged in investigating the 

 structure of the North- West Highlands, and especially among those who did not concur 

 in Murchison's explanation of the phenomena exhibited there, it was a growing belief 

 that great overthrusts had been largely instrumental in producing the remarkable strati- 

 graphical relations of the rock masses of that region. After a most careful detailed 

 examination of the ground by the Geological Survey, the existence and importance of 

 such thrusts was not only placed beyond a doubt, but a variety of additional remarkable 

 structures were discovered, which open up new fields of investigation to the physical 

 geologist.* 



It occurred to some of my colleagues and myself, after studying these great problems 

 in the field, that experiments might be made to throw light on the work by seeking to 

 imitate in the laboratory the processes we believed to have been in operation in our wild 

 North-West Highlands at an ancient geological period. 



With the approval of the Director-General of the Geological Survey, I accordingly 

 instituted a series of experiments on these lines. They were conducted at different times 

 during the last two years at Grange, in Linlithgowshire, where all the requisites for the 

 work were ready to hand. 



The researches, which differed in several particulars from those of former experi- 

 menters in this department, were attended with marked success. The structures obtained 

 in the experiments showed a striking similiarity to those observed in the field, and as the 

 results are otherwise new and important, I now submit them to the Royal Society of 

 Edinburgh. 



The first part of the following paper will be devoted to a description of the principal 

 experiments, and the structures to which they gave rise. As the results obtained are 



* Since this paper was read, a detailed account of the structure of the North -West Highlands has heen published 

 in the " Report on the Recent Work of the Geological Survey in that region, based on the Field Notes and Maps of 

 Messrs B. N. Peach, J. Home, W. Gunn, C. T. Clough, L. Hinxman, and H. M. Cadell" (Quart. Jour. Geol. Soc, 

 August 1888, pp. 378-441). 



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