DYNAMICAL GEOLOGY, 315 



obtained types of folding and deformation which coincided 

 with many of those represented in nature. The first account 

 of Daubree's results appeared in 1878, and in the same year 

 Professor Favre of Geneva published his illustrations of clay 

 strata which had been placed upon a stretched band of 

 caoutchouc, and thrown into folds on the contraction of the 

 elastic basis. In 1888, Mr. Cadell carried out a series of 

 pressure experiments and attained excellent imitations of the 

 tectonical disturbances in mountain-systems. An attractive 

 experimental elucidation of the Appalachian mountains was 

 given by Mr. Bailey Willis in his work entitled The Mechanics 

 of Appalachian Structure. 



All those experimentalists have demonstrated that under 

 strong lateral pressure the material is not only plicated but is 

 fissured and faulted in many different ways, and geologists 

 generally are inclined to think that Professor Heim has not 

 allowed sufficiently for the complicating effects of crust- 

 dislocations. 



The geological significance of fissures and faults was fully 

 realised by the Wernerian School; this was only to be 

 expected, since the foundation of Werner's doctrines was 

 his intimate knowledge of the vein-rock that occurred in the 

 crevices and fissures of the crust, and his careful observation 

 of the relative displacements of the rock on the opposite sides 

 of fault-fissures. From time to time special works on faults 

 have appeared in mining literature. One of the best known 

 earlier works is Carnall's description of the fissures in the 

 Carboniferous district of Silesia, published in 1836; numerous 

 special papers on the British mining districts are included in 

 the Reports of the Geological Survey; and Kohler in 1886 

 published a valuable monograph, entitled Die Storungen der 

 G tinge, Flotze und Lager. 



The faults in mountain-regions were examined by De la 

 Beche, Sedgwick, Thurmann, Harkness, and many others, and 

 their origin commonly ascribed to contraction and mechanical 

 strain; William King explained them as due to processes of 

 crystallisation. The mechanical strains in the crust during 

 mountain-making are undoubtedly the most important factor, 

 and Professor Daubree imitated the effects of strain in a series 

 of experiments. He subjected plates of glass, pieces of rock, 

 and wax prisms to torsion and to vertical and lateral pressures, 

 and produced fissures and displacements which could bear 



