BREAKS IN THE GEOLOGICAL RECORD. 53 



unbroken succession must have existed at one time. We are 

 compelled to believe that nowhere in the long series of the 

 fossiliferous rocks has there been a total break, but that there 

 must have been a complete continuity of life, and a more or 

 less complete continuity of sedimentation, from the Laurentian 

 period to the present day. One generation hands on the lamp 

 of life to the next, and each system of rocks is the direct off- 

 spring of those which preceded it in time. Though there has 

 not been continuity in any given area, still the geological chain 

 could never have been snapped at one point, and taken up 

 again at a totally different one. Thus we arrive at the con- 

 viction that continuity is the fundamental law of geology, as it 

 is of the other sciences, and that the lines of demarcation between 

 the great formations are but gaps in our own knowledge. 



CHAPTER V. 

 CONCLUSIONS TO BE DRAWN FROM FOSSILS. 



We have already seen that geologists have been led by the 

 study of fossils to the all-important generalization that the vast 

 series of the Fossiliferous or Sedimentary Rocks may be divided 

 into a number of definite groups or " formations, " each of which 

 is characterized by its organic remains. It may simply be 

 repeated here that these formations are not properly and 

 strictly characterized by the occurrence in them of any one par- 

 ticular fossil. It may be that a formation contains some 

 particular fossil or fossils not occurring out of that formation, 

 and that in this way an observer may identify a given group with 

 tolerable certainty. It very often happens, indeed, that some 

 particular stratum, or sub-group of series, contains peculiar 

 fossils, by which its existence may be determined in various 

 localities. As before remarked, however, the great formations 

 are characterized properly by the association of certain fossils, 

 by the predominance of certain families or orders, or by an 

 assemblage of fossil remains representing the " life " of the 

 period in which the formation was deposited. 



Fossils, then, enable us to determine the age of the deposits 

 in which they occur. Fossils further enable us to come to very 

 important conclusions as to the mode in which the fossiliferous 

 bed was deposited, and thus as to the condition of the particular 

 district or region occupied by the fossiliferous bed at the time 

 of the formation of the latter. If, in the first place, the bed 



