248 Scientific Geology. 



supposed uniformity has been often broken in upon. For if the 

 geologist can explain how the operation of natural laws might de- 

 stroy races of plants and animals, he must admit a special mirac- 

 alous interference in the creation of new ones. The resemblances 

 between the plants and animals in each of the divisions of the strata, 

 that have been mentioned, even to the very limits of each division, 

 and the suddenness of the change that then takes place in their char- 

 acters, preclude the idea, so much of a favorite with certain philoso- 

 phers, that all was the result of a gradual metamorphosis. Now if we 

 thus ascertain that God has specially interfered with the operation of 

 natural laws in the instances under consideration, the presumption is, 

 that he may interfere again, whenever the good of his universe de- 

 mands. Thus do we get rid of a host of atheistical objections, with 

 which the student of natural theology finds his path encumbered. 

 It would have been well, if some, who can see nothing but atheistical 

 tendencies in the principles of geology, had recollected, before filling 

 their pages with uncandid vituperation of this science and its culti- 

 vators,* that it is the only science whose principles could furnish 

 such a refutation. 



I have here entered only upon the limits of a wide field. I can- 

 not proceed farther. The great interest which every reflecting man 

 feels in speculations of this kind, and the expectation of being misun- 

 understood if I entered into no explanation, (should these labors be 

 made public,) have led me to venture thus far. 



5. GRAYWACKE. 



This term, it is well known, has occasioned much perplexity in 

 geology ; and on many accounts, besides its cacophony, it would be 

 well perhaps to expunge it from the science. Yet I could find no 

 term more convenient, as a sort of index, to an interesting group of 

 rocks, partly chemical and partly mechanical in their structure, 

 occurring in several places in the eastern part of Massachusetts. 

 The varieties included in the group are quite numerous ; and some 

 of them exceedingly unlike the others in composition and appear- 

 ance. Among them all it may perhaps be doubted, whether the ex- 

 act classical graywacke of Werner can be found. But later geolo- 



* See Perm's Comparative Estimate of the Mineral and Mosaical Geologies, 2 

 vols. 8vo. 



