TRANSITION ROCKS. 13 



tion 1 ' was theoretical ; but it is upheld by as many proofs as 

 any other acquired portion of geological knowledge. As 

 regards the objection to the term Transition, that it is un- 

 natural, inasmuch as the rocks of this class pass into the infe- 

 rior and more crystalline strata, and in the upper parts into 

 those of secondary formation, it may be asked — Where is the 

 series of rocks, which, however distinct and separate from 

 its associated formations it may appear to be in one coun- 

 try, has not been observed in other localities to alternate 

 with and pass into them ? If in all cases, however, these 

 appearances were considered hostile to forming arrange- 

 ments of the globe's strata into great divisions, it is evi- 

 dent that no classification could be formed from the rela- 

 tive superposition of strata, and that one from some other 

 system of phenomena would be necessary. Though these 

 transitions of strata into each other, however, are conspi- 

 cuous, there is still no reason why such transitions should 

 be considered as affording a reason that from " gisement" 

 strata should not be arranged. When viewed on the large 

 scale, that on which all geological appearances ought to 

 be viewed, the series which, from superposition, is to be 

 acknowledged as of one formation, is also, from its being 

 characterized by one or more classes of fossilized organic 

 bodies, and in many instances by a wonderful similarity 

 of mineral character, to be considered as the uninterrupted 

 production of a certain geological epoch. The mineral 

 characters of the transition rocks which occur in the 

 Lothians, are limited. The Grey wacke is, in general, a fine 

 aggregate of minute grains of quartz and Lydian-stone, im- 

 bedded in a base approaching to clay-slate, and containing 

 scales of mica very generally distributed through it. In 

 size, the components of the grey wacke vary ; they occur of 

 all magnitudes, between that of the smallest sand and a fine 



