CHAPTER I. 



INTRODUCTION. 



Design of the work. — Previous state of geological knowledge.— -Order of the older 

 fossiliferous strata.— Interval to be filed up, between the secondary deposits 

 previously described, and the older slaty rocks. — Origin of this inquiry, and 

 method pursued in following it out. — General view of the oldest fossiliferous 

 deposits. 



The chief design of the present work is, to fill up an interval in geological history, 

 by describing certain strata, which, although they occupy a considerable thickness in 

 the crust of the globe, and connect the secondary deposits with the older slaty rocks, 

 have never yet been adequately examined. 



A few words will explain the previous condition of this subject. — When the materials 

 of the earth's crust first became a subject of study, they were viewed principally with 

 reference to their mineral characters ; but the attention which was afterwards directed 

 to the imbedded animals and plants, gradually produced a revolution in the science, and 

 gave birth to what is now the largest and most important part of Geology. Since 

 the period when Smith in England, and Cuvier and Brongniart in France, first identi- 

 fied strata by their fossils, a most rapid progress has been made in the application of 

 this method of testing the age of rocks. 



Sixteen years have now elapsed since Conybeare and Phillips, in their Outlines of the 

 Geology of England and Wales, presented us with a connected view of the succession of 

 the sedimentary British deposits, from the most superficial to those which support the 

 carboniferous system ; and, in the succeeding years, great and important additions have 

 been contributed to our acquaintance with the youngest or tertiary deposits particularly 

 by Mr. Lyell. 



But this method has not been so extended as to carry the chronological succession 

 below the Old Red Sandstone ; partly, perhaps, from a preconceived opinion, that few 

 organic remains were likely to be detected in these formations • partly from the belief, 

 founded on just but inadequate observation, that the many mutations which these older 

 rocks had undergone, must have nearly obliterated the evidences of their origin, whether 

 consisting in a clear order of superposition, or in distinctness of zoological contents. 



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