166 CHLORITE SCHIST. 



ceeded by some other, and no stratum occupying more 

 than a few feet, while many do not exceed two or 

 three inches in thickness. 



The leading strata which give the character to the 

 whole series, are the following, placed as nearly as 

 possible with a regard to their relative importance,, or 

 to the spaces which they respectively occupy. The 

 first is a schist, thickly and imperfectly fissile, consist- 

 ing of schistose chlorite and felspar alone, or of these 

 minerals with hornblende or with actinolite super- 

 added. By the increase of the actinolite or of the 

 hornblende, this stratum becomes so compact as 

 scarcely to be distinguished from a hornblende or an 

 actinolite schist ; into which it seems ultimately to 

 pass. Quartz rock is next in quantity, varying much, 

 both in its colour and texture, so as to present its 

 usual modifications when in an independent situation. 

 Next in order is scaly chlorite schist, arenaceous, or 

 silky, and either flat or minutely undulated, splitting 

 into thin laminae, and generally tender where exposed. 

 Micaceous schist forms the last of the essential beds 

 of this series ; being always flat and fissile, and fre- 

 quently presenting a greenish hue, so as at length to 

 pass into the preceding rock. These two last beds 

 rarely exceed a few inches in thickness, and do not 

 together seem to occupy a twentieth part of the 

 whole; while, in some places, the simple hornblende 

 schist predominates over the compound chlorite schist, 

 almost usurping its place in the series. The usual 

 order of arrangement is that of a repeated alternation 

 of every member ; but the micaceous schist is gene- 

 rally next to the quartz rock, and the thin chlorite 

 schist accompanies the thick and compound variety. 

 Thus the contrast between beds of different dimen- 

 sions^ with the perpetual interchange of colour and 



