24 THE OKIGIN A^^D ALTERATION OF ROCKS. 



The views of sedimentation have been pushed so far that one wonders if 

 Strabo, after he had described the volcanic characters of Vesuvius, was not 

 told by his cotemporaries that it was all a mistake — that the peculiar char- 

 acter of the rocks was owing to chemical deposition or to mechanical sedi- 

 ments; that all showed the slow accumulations of millions of years on a slowly 

 subsiding sea-floor ; that the whole had been buried many miles under the 

 accumulating sediments, rendered plastic, causing dikes to be formed; that 

 all the different rocks passed by insensible gradations into one another, etc.; 

 and that, finally, the whole mountain was carved out by the slow process 

 of the removal of the sediments, and was undoubtedly, owing to the crys- 

 talline character of its rocks, one of the earliest formations of the globe. 



In working in regions of crystalline rocks, the principles should be used 

 that one would employ in studying districts in which modern volcanic action 

 has existed, as about Naples, Mount Etna, Iceland, western North and South 

 America, and Japan. 



If this is done, and the older districts are examined by the aid of the light 

 given by the modern eruptive formations, the writer believes that the pres- 

 ent obscurity enveloping the former would be cleared away. The greatest 

 difficulties in the study of such regions seem to have been in the theoretical 

 views of the observers themselves. The question regarding such rocks 

 should be, what are the facts, and not what are the theories. 



It seems to the writer clear that the earlier formations of which Ave have 

 any record in the earth's crust were not derived from the waste of earlier 

 lands, but rather that they are for the most part eruptive, if not portions of 

 the first formed crust; and that the fragmental portions were eruptive ashes, 

 or were derived from the waste of eruptive material.* 



The burden of proof rests upon the advocate of ancient destroj^ed conti- 

 nents, to show tliat the materials which he supposes came from such lands 

 could not have been derived from the eruptive action of that early day. 



The term eruptive, or volcanic, has been applied in this paper to all rocks 

 coming from beneath the surface, showing signs that they have been in a 

 fluid condition, — whether ancient or modern, — for nature has not, to my 

 belief, drawn any line in her rocks between the younger volcanic and the 

 older plutonic forms, but all form a continuous and harmonious whole. 



* Gcikie, Text Book of Geology, pp. 12, 13. 



