296 GENERAL COMPARISON OF 



like gneiss in an undulating irregular manner determined 

 in some measure by the chloritic laminae. 



With regard to the two last named rocks, it is evident 

 that we have no terms under which they can with pro- 

 priety be arranged. It is true that the former possesses a 

 certain analogy to the compound hornblende schist, and 

 the latter to chlorite schist; but the differences, both 

 in the relative proportions and in the disposition of the 

 ingredients, are in both cases so great as perhaps to justify 

 distinct appellations; a claim further supported by the 

 peculiarity of their geological connexions. The invention 

 of new terms is however a delicate task, and their recep- 

 tion is so much more frequently the consequence of 

 authority than fitness, that it is better left to others, or 

 to a time when the necessity will be more generally felt. 



To these must be added the following substances, which 

 do not in strictness belong to either division, though very 

 nearly akin to the hornblende schists. 



1. Schistose actinolite, spicular or scaly in the fracture. 



2. Actinolite and felspar, the two ingredients occurring 

 in a great variety of proportion, with consequent varia- 

 tions in the aspect of the rock. 



3. Actinolite and felspar, with hornblende, or with black 

 mica) or with both, superadded. 



In terminating the account of the Chlorite series, it 

 is necessary to add that some rocks of a different nature, 

 not yet enumerated, occur in some parts of the tract which 

 it occupies. As it alternates once with the clay slate 

 of the Slate isles near its north-western boundary, so, in 

 the neighbourhood of Crinan, a somewhat extensive range 

 of fine clay slate and of graywacke beds, are found alter- 

 nating with it. These rocks occur also in other places, 

 but always in very minute portions. If these alternations 

 detract nothing from the general integrity of the Chlorite 

 series, they add another example to the numerous unre- 

 corded associations in which clay slate and graywacke are 



