Prof. Beck on Igneous Action, as exhibited in New York. 343 



In reviewing the facts set forth in this paper, we arrive at the 

 following conclusions, viz. 



1st. That if it is admitted that the original protrusion of granite 

 was due to igneous action, and if to this is to be ascribed the 

 crystallization of the minerals found in the primary beds and 

 strata, these must in many cases have been a second time sub- 

 jected to a high temperature, — high enough at least to cause the 

 partial fusion ofthese minerals. 



2d. That at later geological periods the presence of water be- 

 came another, and perhaps new condition, of the great igneous 

 agency, and that hence serpentine with its large proportion of 

 water was one of the results. 



3d. That the presence of water, known to be an almost invari- 

 able condition of modern volcanic action, is proved to have been 

 no less so during the periods when the eruptions of the trappean 

 rocks took place. 



Finally, I have endeavored to show that as we proceed to the 

 interior of the earth there are arrangements of mineral forms 

 quite different from those which characterize the lowest of the 

 primary rocks as they appear on the surface. Now I think it 

 conceivable that the character of the igneous eruptions may have 

 been connected with circumstances attending the different depths 

 to which the refrigeration, and consequently the solidification of 

 the crust may have extended. When the granitic deposits had 

 been but partially solidified, fissures and cracks in the crust would 

 be followed by injections of the same mineral ingredients, in 

 some instances perhaps sparingly mixed with those below. Hence 

 the formation of true granitic veins with their accompanying 

 minerals, during such a state of things, might be easily accounted 

 for. But as the solidification extended towards the interior, the 

 erupted matter would exhibit a different aspect, owing perhaps in 

 part to the new agencies which were brought into action, but 

 chiefly to a real difference in the mineral matter or composition, 

 which we have reason to believe exists in different parts of the 

 central nucleus, or at different distances from the surface. 



