SOME MODERN ASPECTS OF GEOLOGY. 645 



soil it readily took root and flourished like a vigorous tree, bear- 

 ing rich, fruit and sending its seeds into every land upon the 

 earth where knowledge is sought for. 



At first progress was necessarily slow, mistakes were frequent, 

 and a general interest in the subject was almost lacking. But as 

 one point after another was gained, and as a deeper insight into 

 the problems presented was secured, the number of workers stead- 

 ily increased. The patient labors of such pioneers as Zirkel, 

 Vogelsang, and Rosenbusch can never be forgotten by those who 

 can now avail themselves of their years of toil in a few months. 



Interesting and surprising results were secured at the outset 

 by the new science, but they were mineralogical rather than geo- 

 logical in their bearing. It is only now, after thirty years of 

 preparation, that the time is fully ripe for the application of the 

 new petrography to some of the deepest questions of theoretical 

 geology. This it is which affords almost the only hopeful means 

 of dealing with the records of the crystalline strata of the earth, 

 which undoubtedly contain the longest, as they do by far the dark- 

 est, chapter of its history. What paleontology has already done 

 and is still doing for the more superficial strata in which organic 

 remains are preserved, the microscope must do for the crystalline 

 rocks, whether volcanic, plutonic, or metamorphic. These con- 

 tain their own life-histories, written in characters which need 

 only to be carefully studied in order to be properly interpreted. 



The purely mineralogical services of the microscope need not 

 here concern us, but it may be pertinent to inquire, What spe- 

 cific classes of facts has this instrument disclosed and what new 

 ideas has it suggested that entitle it to so high a consideration by 

 those who are interested with the broader problems of the earth's 

 history ? To this inquiry we may answer : 



1. The microscope has shed light into darkness ; and, by its 

 promise of results, has stimulated an enthusiastic cultivation of a 

 most important but hitherto neglected field. 



2. It has shown us that the internal structure of the common- 

 est pebble is not less admirable, delicate, and exquisitely beautiful 

 than that of a living organism. 



3. It has already thrown much light upon the origin of many 

 of the crystalline rocks — both massive and schists — by allowing 

 us to judge of the conditions under which they must have been 

 formed. 



4. Most wonderful of all, it has taught us that the components 

 of the " everlasting hills " are not mere masses of dull, unchange- 

 able, inert matter, but that, in so far as constant change of form 

 and composition to accord with altered conditions is a sign of life, 

 they live. 



Any single one of the four points which I have here enumer- 



