AUGILLACEOUS SCHIST. 185 



rather than things, and to whom authority stood in 

 place of reasoning and observation both, easily trans- 

 ferred the term graywacke to all the argillaceous schists 

 of similar structure ; and the word transition becoming 

 a ready excuse for neglect, or a substitute for know- 

 ledge, these strata became graywackes and transition 

 rocks whenever it was convenient,, either for the system, 

 or for the observer's ease or ignorance. I should think 

 this criticism misplaced, had it not been necessary for 

 the elucidation of a most vexatious obscurity in geo- 

 logical writings. In reflecting on this abuse of terms, 

 we are almost inclined to wish that the business of 

 Geology could be carried on without them. There 

 would at least be fewer writers, when descriptions 

 must be substituted for phrases ; nor would so much 

 time be occupied in undoing the knots which ignorance 

 has tied, and which have made a warfare of a peace- 

 able pursuit. 



The examination of Nature confirms the propriety 

 of the arrangement which I have thus adopted. There 

 is no extensive mass of fine schist, or clay-slate^ in 

 which the coarse, or graywacke, does not occur, while 

 the reverse is also true : arid, in all cases, the geolo- 

 gical relations are the same, or the identity perfect. 

 Moreover, the two structures pass into each other by 

 insensible gradations ; sometimes vertically, in a bed 

 or series of beds, and at others laterally, in the same 

 bed : while what is true of the larger tracts of argilla- 

 ceous schist is equally so of the smaller masses found 

 among the primary strata. And the priori reasoning 

 supports as it explains the facts; as they are explained 

 also by the analogy of the sandstones of varying tex- 

 ture : both of them being aqueous deposits of fine and 

 coarse materials, thus separated by the action of water. 

 The geological uniting of these, lastly, equally justi- 

 fies the present arrangement. 



