RISE OF PETROLOGY AS A SCIENCE 249 



tant questions. It is remarkable, also, how keen were 

 the observations that the geologists of those days made 

 upon the rocks, as to their component minerals and 

 structures, aided only by the pocket lens. Many ideas 

 were put forward, the essentials of which have persisted 

 to the present day and have become interwoven into the 

 science, whereas others gave rise to contentions which 

 have not yet been settled to the satisfaction of all. At 

 tunes in these earlier days the microscope was called into 

 use to help in solving questions regarding the finer 

 grained rocks, but this employment, as Zirkel has shown, 

 was merely incidental, and no definite technique or 

 purpose for the instrument was established. 



On the other hand, the fact that up to the middle of the 

 last century a large store of information relating to the 

 occurrence of rocks, and to the mineral composition of 

 those of coarser grain, and somewhat in respect to their 

 structure, had been accumulated, caused attempts in one 

 way or another to find means of coordinating these data 

 and to produce classifications, such as those of Von Cotta 

 and Cordier. The history of these attempts at classifi- 

 cation, before the revelations made by the use of the 

 microscope had become general, has been admirably 

 reviewed by Whitman Cross 1 and need not be further 

 enlarged upon here. 



That a considerable amount of work was done along 

 chemical lines also is testified to by the publication of 

 Roth's Tabellen in 1861, in which all published analyses of 

 rocks up to that date were collected. "What was accom- 

 plished during this period was done chiefly on the con- 

 tinent of Europe, and little attention had been paid to the 

 subject of rocks either in America or in Great Britain 

 even so late as 1870 Geikie remarks, as referred to by 

 Cross, 2 that there was no good English treatise on 

 petrography, or the classification and description of 

 rocks. In this country still less had been accomplished, 

 interest being almost wholly confined to the vigorous and 

 growing sciences of geology and mineralogy. This was 

 natural, for mineralogy is the chief buttress on which the 

 structure of petrology rests and must naturally develop 

 first, especially in a relatively new and unexplored 

 region, whose mineral resources first attract attention. 



