92 ON THE TERM " TRANSITION." [Ch. VllI 



matious were accumulated in waters resembling those of tlie present ocean, 

 except at certain intervals, when, from causes wholly unexplained, a par- 

 tial recurrence of the " chaotic fluid" took place, during which various 

 trap rocks, some highly crystalline, were formed. This arbitrary hypothe- 

 sis rejected all intervention of igneous agency, volcanoes being regarded 

 as modern, partial, and superficial accidents, of trifling account among the 

 great causes which have modified the external structure of the globe. 



Meanwhile Hiitton, a contemporary of Werner, began to teach, in 

 Scotland, that granite as well as trap was of igneous origin, and had at 

 various periods intruded itself in a fluid state into different parts of the 

 earth's crust. He recognized and faithfully described many of the phe- 

 nomena of granitic veins, and the alterations produced by them on the 

 invaded strata, which will be treated of in the thirty-third chapter. He, 

 moreover, advanced the opinion, that the crystalline strata called primi- 

 tive had not been precipitated from a primaeval ocean, but were sediment- 

 ary strata altered by heat. In his writings, therefore, and in those of his 

 illustrator, Playfair, we find the germ of that metamorphic theory which 

 has been already hinted at in the first chapter, and which will be more 

 fully expounded in the thirty-fourth and thirty -fifth chapters. 



At length, after much controversy, the doctrine of the igneous origin of 

 trap and granite made its way into general favor ; but although it was, in 

 consequence, admitted that both granite and trap had been produced at 

 many successive periods, the term primitive or primary still continued to 

 be applied to the crystalline formations in general, whether stratified, like 

 gneiss, or unstratified, hke granite. The pupil was told that granite was 

 a primary rock, but that some granites were newer than certain secondary 

 formations ; and in conformity with the spirit of the ancient language, to 

 which the teacher was still determined to adhere, a desire was naturally 

 engendered of extenuating the importance of those more modern granites, 

 the true dates of which new observations were continually bringing to hght. 



A no less decided inclination was shown to persist in the use of the 

 term " transition," after it had been proved to be almost as faulty in its 

 original apphcation as that of flotz. The name of transition, as already 

 stated, was first given by Werner, to designate a mineral character, inter- 

 mediate between the highly crystaUine or metamorphic state and that of 

 an ordinary fossiliferous rock. But the term acquired also from the first 

 a chronological import, because it had been appropriated to sedimentary 

 formations, which, in the Hartz and other parts of Germany, were more 

 ancient than the oldest of the secondary series, and were characterized by 

 peculiar fossil zoophytes and shells. When, therefore, geologists found 

 in other districts stratified rocks occupying the same position, and inclosing 

 similar fossils, they gave to them also the name of transition^ according 

 to rules which will be explained in the next chapter ; yet, in many cases, 

 such rocks were found not to exhibit the same mineral texture which 

 Werner had called transition. On the contrary, many of them were not 

 more crystalline than different members of the secondary class ; while, 

 on the other hand, these last were sometimes found to assume a semi- 



