GENERAL REMARKS ON GNEISS. 227 



in this case more than in that of granite, for creating 

 a new species. While the component parts vary in both 

 cases, the continuity and geological relations of both the 

 rocks continue unaltered. 



On a first view the varieties in the aspect of gneiss are 

 so numerous that it would appear impossible to refer them 

 all to the following list. Yet, when strictly examined, it 

 will be found that these diversities, as in the case of 

 granite, arise from variations in colour, proportion, dispo- 

 sition, and size of the constituent parts ; circumstances 

 evidently capable, under their possible combinations, of 

 producing varieties that may fairly be considered infinite. 



I have only to add as a preliminary to the synoptic 

 table that the second division contains two subdivisions, 

 and that the third presents subdivisions of structure similar 

 to the first, although not sufficiently constant, or ex- 

 tensive in a geological view, to require a formal arrange- 

 ment in the present sketch. 



