CHAPTER VI. 



THE CRITERIA AND PRINCIPLE D BY AUTHC THE COR- 



RELATION OF THE VARIOUS PARTS COMPOSING THE GROUP, 

 WITH OBSERVATIONS ON SOME METHODS OF CORRELATION. 



HISTORICAL ES. 



The earlier American geologists took their ews o: ~ion 



and princi; correlation mainly from E to authors. An 



the latter Dr. John Woodward m y in t\ :eenth centui 

 i tural E i .story of the Barti 



That the stone and other terrestrial matter in France, Flanders, Holland, Spain, 

 Italy, Germany, Russia, and Sweden were distinguished, in strata, or lamer* as it is in 

 England : that these strata were divided by parallel layers ; that there were inclosed 

 in the -i-one and alJ the other denser kinds of terrestrial matter great numbers of the 

 shells and other productions of the sea in the same manner as in that of this island. 1 



- one, of the ear] ations of stratified and fossil iferous 



rocks. rode and indefinite as compared with modern eorrela- 



bat the general method of comparing stratified fa ous rocks be- 



>e they are stratified and fossiliferoos was inaugurated. 

 Dr. Abraham W ematic form to desc 



tive geology in the latter part of the eighteenth century; while about 



me Prof. William Smith, in England, applied organi- 

 mains in geologic investigation, and correlated formations in various 

 parts of the British islands by their contained fossils. A little later 

 Baron < r was establishing in France the grea* oles 



of the succession of varying organic remains in 

 differentiation from living forms. 



Ma/ lure. — In Ameriea Mr. William Mac! are was among the first to 

 take advantage of the principles of classification enunciated by Dr. 

 ner, and we find the correlations made by him in preparing his 

 geological maps were based entirely upon lithologic and strati graphic 

 evic This is stated in the first paragraph of the introduction to 



his paper : * 



Necessity dictates the adoption of some system. 80 far as respects the classifica- 

 tion and arrangement of names the Wernerian appears to be the most suitable, first, 

 because it is the most perfect and extensive in its general outlines, and secondly, 



'An E*mj i«-B-ar4t a SatiznJ Hjfto.j«tl>*E*TrtffliTtnwL'iilBrfj» Umam^UtA^. 

 Kllitii riii>«a#« tl^C1f^iigrftfafcUBit^S<da**fcx^ta«atorjrfa6t*tofflr*i mm§L Am.PhiL&&c 

 T«L€,Um, w .4H 



301 



