446 SKETCH TOWARDS A 



strata: not only because I cannot trust the information 

 collected by such observers, under such hypotheses, or 

 because my own personal knowledge is insufficient, and 

 that I do not see what is gained by philosophizing 

 through the eyes of others, but because I have proved 

 that we know nothing of those marine strata which 

 are of parallel time to the coal and the lignites. But 

 the principles of grouping seem simple, as far as any 

 deposits are truly vertical in position ; without which, 

 it is plain that we can at present do nothing. And if 

 geologists should receive them, time may produce what 

 we yet have not, and give us at least something nearer 

 to the truth. It is for this very purpose that I have 

 laboured to state our ignorance as well as our know- 

 ledge, and also its exact nature: it is not the easiest 

 task in science, as every one knows: while unfortunately 

 it is also a considerably offensive undertaking, to those 

 who prefer the semblance and the reputation of know- 

 ledge to its possession. 



A sandstone and a shale, singly or alternating, mark 

 the degradation of terrestrial rocks; a limestone indi- 

 cates the production of subaqueous animals under 

 tranquility in the earth: and a coal denotes where its 

 surface then was. Suffering the inferior coal deposit 

 to remain as a single group, the space between two 

 carbonaceous strata, and these being also untransported 

 ones, is therefore a group, of which we are sure: as 

 we are in the case of a single and separate parallelism 

 among the inferior strata of the earth. If there are to 

 be large groups on any other principles than these two, 

 let some one else point those out; for I cannot. And 

 if smaller ones are desired, the principles seem to be 

 these. First, that any great mass of strata, in truly 

 and tangibly vertical order, geologically speaking, which 

 is predominantly or conspicuously calcareous, marks a 



