2$6 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



and methodical investigation of the earth's crust may be said 

 to have begun towards the end of the eighteenth century. 

 The careful sections of the Thuringian district prepared by 

 Lehmann and Fuchsel initiated a new direction in crust- 

 physics, and fore-shadowed* the special work undertaken by 

 stratigraphical research in the present day, to find out the 

 actual distribution of the rocks in the ground so far as they 

 are at present exposed to view, and if they do not occur in 

 undisturbed horizontal succession, to determine what dis- 

 placements they have suffered, and reconstruct as nearly as 

 possible a true mental picture of the sequence of events, the 

 original distribution of the various sediments in time and 

 place, the subsequent movements secular or paroxysmal, and 

 the character of the resultant deformation of rock-particles 

 and rock-masses. 



Werner and his scholars contributed to field research many 

 of its precise terms and methods. They examined the rocks 

 with respect to strike and dip ; alternations of strata ; mutual 

 stratigraphical relations in vertical and horizontal directions; 

 the displacements effected along fault-lines; upheaval, curva- 

 ture, bending and folding of rocks. The terminology which 

 they applied very often betrays the close connection which 

 existed between the mining industry and the beginnings of 

 stratigraphy. The mines, the minerals, and any evidences of 

 rock-displacement discovered during the mining operations 

 were the sources of knowledge from which Werner taught, and 

 as his scholars gradually extended their field of vision, and the 

 glance of a Humboldt or a Leopold von Buch became world- 

 wide, the early impressions and familiar terms of student days 

 were grafted into the more ambitious conceptions and general- 

 isations with which such men enriched the systematic study of 

 the earth's crust. Many mining terms have thus been adopted 

 into geological literature, although the original significance has 

 been in some cases considerably modified. 



Pallas and De Saussure gave the first more exact accounts of 

 the structure of mountain-systems, and early in the nineteenth 

 century important advances were made by the investigations of 

 Ebel, Studer, Escher, Elie de Beaumont, and others in the 

 Alps, those of Voigt and Heim in the Thuringian Forest, of 

 Merian and Thurmann in the Swiss Jura Chain, of De la 

 Beche in Cornwall and Devonshire, of Sedgwick and Murchison 

 in Wales, and of the brothers Rogers in Pennsylvania. The 



