12 Mr HOPKINS, ON RESEARCHES IN PHYSICAL GEOLOGY. 



With these hypotheses then respecting the nature of the elevatory 

 force, and the constitution of the elevated mass, I shall proceed in the 

 next section to investigate the directions in which fissures will be 

 formed in it when subjected to given internal tensions sufficiently 

 great to overcome the cohesive power which binds together its com- 

 ponent particles. These tensions, so far as this investigation is con- 

 cerned, may either be supposed to be produced by external forces 

 causing an extension of the mass, or by such as prevent that contrac- 

 tion of it which might be conceived to result from the loss of moisture 

 or of temperature. It must be understood however that these internal 

 forces are quite distinct from that sort of molecular action on which 

 any kind of laminated or crystalline arrangement of the component 

 particles may depend. 



