OP CREATION. 



257 



far it is probable, from this condition, that the whole 

 secondary deposit in Europe took place in a sea 

 limited in extent, surrounded, or nearly so, by land 

 to the west and north, and subject to very constant, 

 but inconsiderable changes of level in that direction, 

 though comparatively quiet in its eastern portion, 

 where there was deeper water. Such a condition 

 would seem to account for the great variety and ex- 

 tent of the deposits, the uniformity of some few of 

 them in certain directions, the persistence of some 

 fossils of high organization (as the Ichthyosaurus, 

 &c.) through several distinct divisions, and the ge- 

 neral uniformity of character of the group of fos- 

 sils in some, but not in all districts. If we look 

 upon the whole period as one of transition in the 

 latitude of Europe, and suppose that the axis of dis- 

 turbance was shifting from the north and south to 

 the east and west direction, many of the apparent 

 anomalies of the formations will perhaps disappear. 



Whatever may be the result of speculations of 

 this kind, the fossils of the secondary period certain- 

 ly exhibit a very perfect and beautiful series, possess- 

 ing characters at first difficult to decipher, but al- 

 most always capable of being made out by detailed 

 and careful investigation. 



Observing the indications given by the different 

 and successive groups of organic remains, we can 

 also learn the changes that have taken place in a 

 particular district; and thus, for instance, in Eng- 

 land, we may trace a rapid deposition of limestone in 

 one spot, and mud in another, these being contem- 

 poraneous, but having very different fossils. Each 

 of these, again, was succeeded by other beds of the 



