462 BUTE. GEOLOGY. 



form too strong a distinction; and whether it has a claim 

 to be considered as conferring an exclusive geological cha- 

 racter on any series existing in nature. The analogy be- 

 tween the conglomerated or coarser varieties of the mica- 

 ceous and chlorite schists occurring in the series of Bute, 

 and the graywacke of the argillaceous schists, is striking ; 

 and these may, like that substance, be considered the 

 graywackes of those rocks. It would be superfluous, 

 if not injurious, to make such a distinction in those 

 cases ; as the transition from the most mechanical 

 structure to that which possesses the least of this 

 character, is indefinite ; and the same rule appears 

 advantageously applicable to the latter. In such a 

 case, the geological distinction would be that of argil- 

 laceous schist simply ; comprising every variety of 

 structure in which clay slate and quartz were the 

 fundamental ingredients; the term graywacke being 

 reserved as a mineralogical designation only, or as the 

 name of a species of rock. If a rock of this structure 

 be indeed found in nature, distinct from fine argillaceous 

 schist, and possessed of other geological characters so 

 striking as to confer on it a claim to a distinct place 

 in the history of the earth, it will be worthy of con- 

 sideration whether some geological term ought not to 

 be adopted for distinguishing it from those which are 

 found in the various situations I have formerly described, 

 alternating with common clay slate and with the other 

 primary strata. The term of transition is too hypothe- 

 tical ; and such a distinction, if it really exists, much 

 too difficult of application, to render it of use in this 

 case ; while it must inevitably lead to the practice of 

 concluding, rather than to that of investigating. 



It will perhaps be thought, that in stating the pre- 

 ceding facts, and in deducing the remarks to which 

 they have given rise, confusion has been introduced 

 where the labours of others had established regularity. 

 The facts themselves may even be considered as ex- 



