152 ON THE CHARACTERS AND DISPOSITION 



be argued that such a mass could not have been eject- 

 ed from below. 



In these last cases, there is one circumstance worthy 

 of notice in this question : it is the difference between 

 the manner in which the trap meets the secondary 

 strata, and that in which granite meets the primary. 

 The junctions in Sky are, in many parts,, vertical and 

 very precise ; although there are the usual limited 

 disturbances and penetrating veins. This difference 

 arises from a different condition in the invaded strata? 

 which is confirmed by every other circumstance of 

 difference that attends the passage of veins in both, the 

 appearances at the junctions, and those of the strata 

 themselves. These were noticed before in the case of 

 veins, and they arise from the yielding and flexible 

 nature of the strata in the one case, and their rigidity 

 in the other ; facts fully evinced by the contortions 

 which attend the primary stratified rocks. The very 

 quality of the rocks themselves, independently of soft- 

 ness, may have contributed to these differences; as is 

 proved by the instance in Morven, where the lateral 

 junction of the trap with the gneiss is of a very dif- 

 ferent character from those which take place between 

 it and the secondary strata of Sky. So far therefore 

 from its being proved that the mode of junction be- 

 tween granite and the incumbent strata is not the 

 consequence of eruption, because it does not resemble 

 the junctions of trap in similar cases, these differences 

 are precisely of a nature to confirm that opinion. If, 

 in mechanics, unequal bodies are projected with a 

 common velocity, we infer that two forces have 

 acted ; if the velocities are different, we then inquire 

 whether one force may not have acted on both. It is 

 not probable that Geology will ever be ranked among 



