614 HISTORY OF GEOLOGY. 



bridge, 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 elevatory 

 force, acting simultaneously at every point beneath 

 extensive portions of the crust of the earth. An 

 application of mathematical reasoning to the illus- 

 tration of the phenomena of veins had before been 

 made in Germany by Schmidt and Zimmerman 9 . 

 The conclusions 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 interest- 

 ing points of examination respecting the geological 

 phenomena of fissured districts (G A.) 



Other forces, still more obscure 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 struc- 

 ture of mineral masses has been produced. These 

 forces are probably identical, on the one hand, with 

 the cohesive forces from which rocks derive their 

 solidity and their physical properties ; while, on the 

 other hand, they are closely connected with the 

 forces of chemical attraction. No attempts, of any 

 lucid and hopeful kind, have yet been made to bring 

 such forces under definite mechanical conceptions: 

 and perhaps mineralogy, to which science, as the 

 point of junction of chemistry and crystallography, 

 9 Phil. Mag. July, 1830, p. 2. 



