J. C. Doornik un Fossil Organic Remains. 75 



all we know concerning succession in the primitive formations, 

 directly the result of observations purely geological ? Are we 

 not able to distinguish successive formations in strata, which do 

 not belong to the primitive ? Should we confound the forma- 

 tion of chalk with that of the calcaire grossier, if deprived of 

 the aid of their imbedded shells, when there exists the formation 

 of plastic clay, of molasse and conglomerates of various kinds, 

 intermediate between the strata ? In every formation, from 

 the lowest to that which is uppermost, we perceive a repetition 

 of rocks and strata, whose chemical composition is similar ; that 

 is, siliceous, argillaceous, or calcareous. But the difference in 

 structure is most obvious. The lower formations are crystallized 

 and firm ; whilst the upper are earthy and loose. The interme- 

 diate formations differ from these, as well as from each other, 

 in a manner no less remarkable. A striking character of the 

 transition formation, and which separates it from the primitive 

 and secondary, is seen in the alternation of a series of rocks, 

 in which there is a regular recurrence of similar beds, rendering 

 perfectly obvious, likewise, the limits of this extensive class of 

 rocks. Another characteristic of the same formation exists in 

 the three great formations, which hold nearly the same rank in 

 different parts of the globe. They are, 1*^, Talcose granular 

 limestone, greywacke with anthracite and micaslate ; 9,dly, Sye- 

 nite and porphyry, with crystals of hornblende, and occasionally 

 quartz ; Qdly, Clayslate, greywacke and black limestone. 



The micaslate, with anthracite and clayslate, serves as the 

 connecting points of the transition and the primitive ; whilst, on 

 the other hand, the fine-grained greywackes and porphyries, 

 abounding in the crystals of quartz, cause it to approximate to 

 the secondary. 



The different ages of these formations are likewise indicated 

 by their position. For example, the porphyries of Guanaxuato 

 repose upon bituminous clayslate ; those of Hungary upon a tran- 

 sition micaslate ; whilst those of the Andes of Quito are situated 

 upon primitive rocks. Large masses of greywacke are to be seen 

 in the oldest slate rocks of the transition class ; whilst extensive 

 beds of greywacke arc met with, whose origin is more recent. 

 In fine, the transition class of rocks is distinguishable botii by 

 strucluic and age from the primitive : — the limits of the latter 



