394 THE CAMBRIAN. (bull. 81. 



In connection with the discussion of the presence of organic remains 

 in the rocks the following passage occurs : 



The geological deposits of this country (and probably those of the eastern conti- 

 nent) exhibit grounds for conjecture if not absolute demonstration that the surface 

 of the earth has undergone five general modifications, which no animals survived. 

 Four of these modifications were followed by as many new creations of animals. Also 

 that two new creations of animals succeeded the final depositions of all regular strata. 

 In the whole, there appears to have been five creations of animals at least (perhaps 

 ten) since the primitive m ass of the earth was formed, and a long interval succeeded 

 each creation. 1 



It is also said that the " remains or impressions of plants are limited 

 to coal and coal formations whose relative position is indicated by their 

 rocky associates ; the determination of rocks by their animal relics 

 serves as an index to the position of coal measures or beds. In this 

 concise selection of the most esseutial relics animals alone will be 

 noted which have no backbone nor brains " [invertebrates]. 2 



Under the title of "Geological Equivalents" Prof. Eaton mentions 

 that relative position and mineral constituents were deemed sufficient 

 by Werner for determining geological equivalents. As relative position 

 is the basis of the science, all other circumstances have always been 

 received as auxiliaries only so far as classification is concerned. 3 He 

 reasoned that as rocks can be traced more or less continuously through- 

 out New York and Pennsylvania the data used by Werner are of 

 value; but — 



From a consideration of the cases here referred to, intrinsic characters more definite 

 than any left us by Werner seem to be essential to the progress of the science. The 

 enumeration of mineral constituents of rocks can never be satisfactorily applied. 

 Unorganized matter presents but few characteristics. Naturalists find it a more dif- 

 ficult task to describe by external characters about two hundred and seventy species 

 of minerals than fifty thousand species of plants and a still larger number of ani- 

 mals. 



It is a subject of high congratulation to students in geology of our day that the 

 illustrious Cuvier, aided by the Brongniarts and their coadjutors, have extended the 

 science of organic nature to the science of geology. We are no longer limited to the 

 enumeration of mineral constituents. We find the same organized remains associated 

 with equivalent strata in every part of the earth, though they often extend into 

 several adjoining strata, which are probably contemporaneous or nearly so. 4 



He then proceeds to classify the strata as known to geologists of both 

 continents by means of some of their organic associations in North 

 America. 5 



A few months later he published a paper on " Four cardinal points 

 in strati graphical geology established by organic remains," saying: 



If the identity of the Granular, the Metalliferous, and the Oolitic calcareous rock<, 

 and of the Tertiary marls are established on both continents all intervening strata 

 may be ascertained with great facility. I think that a reference to the following 

 facts will be sufficient to establish their equivalent characters at least. 6 



' Op. cit., p. 48. 6 Op. cit., pp. 136-138. 



2 Op cit., p. 25. • 6 !Four cardinal points in stratiyraphical geology 



3 Geological equivalents. Am. Jour. Sci., vol.21, established by organic remains. Am. Jour 

 1832, pp. 132-13&. Sci., vol. 21, 1832, p. 199. 



4 Op. cit., p. 134. 



