7? Mr HOPKINS, ON RESEARCHES IN PHYSICAL GEOLOGY. 



Let us suppose then, that the fluid mass has risen through the 

 fissure of which Cc is the section, till it has reached the stratum adb. 

 If this stratum have sufficient tenacity and extensibility, and but little 

 adhesion to that on which it reposes, it is easy to conceive that it may 

 be elevated without being broken, if the fluid mass be impelled upwards 

 with sufficient force to overcome the weight of the superincumbent mass. 

 In this case the fluid will necessarily be injected horizontally, as repre- 

 sented in the figure, and so long as the lower surface of the uplifted 

 stratum remains perfectly continuous and unbroken, it is very possible 

 that this injection may extend to any assignable distance without the 



production of vertical dykes, on veins branching from tlie upper surface 

 of the injected bed. In this case there would appear to be no indications 

 of mechanical action from which the geologist of the present day could 

 ascertain whether such bed had been ityected among the beds associated 

 with it, or ejected over the surface acb at a period anterior to the 

 formation of the superincumbent strata. 



The most favorable case we can conceive for the kind of injection 

 we are considering, without the production of the vertical veins above 

 mentioned, is that in which we assume the absence of all adhesion 

 between the uplifted bed and that immediately beneath it ; but even 

 in this case the condition of unbroken continuity in the lower surface 

 of the superincumbent; mass, must be satisfied, not approximately, but 

 accurately ; for if the smallest crevice existed in the uplifted portion, 

 the injected matter would be impelled into it with a force proportional 

 to the enormous pressure to which it would be subjected from the 

 weight of the superincumbent beds; and if the injection should take 

 place under the weight also of a deep sea, the probability of this effect 



