Mr HOPKINS, ON RESEARCHES IN PHYSICAL GEOLOGY. 



41 



SECTION II. 



35. Let us now proceed to apply the results obtained in the last 

 section to the actual case of a portion of the earth's crust, under the 

 hypotheses respecting the action of the elevatory forces and the cohesive 

 power of the mass, which have been already stated, (Introd. p. 11, and 

 Art. 12.) And, first, let us suppose, for the greater simplicity, the surface 

 of the mass acted on to be of indefinite length, and bounded laterally by 

 two parallel lines. If we first suppose the elevatory force to be uniform, 

 it is manifest that the extension, and therefore the tension, wiU be 

 entirely in a direction perpendicular to the length; so that its whole 

 tendency will be to produce longitudinal fissures, or such as are parallel 

 to the axis of elevation. 



^. Formation of Longitudinal Fissures — Their Position and Width 



Complete and Incomplete Fissures. 



36. Let the aimexed diagram represent a transverse section of the 

 elevated mass, and let us suppose it symmetrical with respect to the 

 line CC, and also that the mass below the horizontal line AB remains 



perfectly undisturbed. The cavity ACBD, containing the fluid through 

 the medium of which the elevatory force is supposed to act on the 

 lower surface of the elevated mass, (see p. 10), may either be supposed 

 to have existed previously to the action of the elevatory forces, or to 

 have been partly produced by them. 

 Vol. VI. Part I. F 



