Introduction to Geology* 63 



the chalk. The utility of this distinction has become more 

 apparent since the discoveries which the last few years have 

 produced ; and the arrangement is further authorised by the 

 peculiar character of those numerous tribes which people these 

 beds, and which were called into existence subsequently to the 

 chalk. 



It was afterwards perceived that the Secondary class re- 

 quired division in that part of the series which approached 

 nearest to the Primary, or earliest-formed rocks ; because 

 there appeared an intermediate class, which, notwithstanding 

 they contained organic remains, possessed a structure that 

 allied them to the Primitive. On these the name of Tr^ansi^ 

 tion, or Intermediate, was conferred. 



There were thus founded four principal divisions of rocks, 

 Primary, Transition, Secondary, and Tertiary. M. Al. de 

 Humboldt adheres to this order in his Table of Geological 

 Formations, which enriches the work of Baron Cuvier ; and 

 most Continental and English geologists pursue the same 

 system. 



Werner, the celebrated mineralogist of Germany, divided 

 the formations into Primaiy and Floetz only, which latter in- 

 cludes the Transition and Secondary. Mr. Weaver and Dr. 

 Macculloch have adopted a similar arrangement in their clas- 

 sification of rocks. 



Mr. Coneybeare, in his admirable Introduction to the Geo^ 

 ^^Sy 9f England and Wales, makes use of another system, 

 founded on the position of the strata and rocks, under five 

 heads : 1 . Superior order ; 2. Supermedial order ; 3. Medial 

 order ; 4. Sub-medial order ; 5. Inferior order. This arrange- 

 ment has the single recommendation of being divested of all 

 theory. 



The first is the Tertiary class above mentioned, or that which 

 Werner named the Newest Floetz class ; the second is the Se- 

 condary class, the Floetz of Werner, and the Sedimentary of 

 others ; the third and fourth comprise the Transition, or inter- 

 mediate class ; and the fifth the Primitive, or Primary Rocks. 



From its apparent want of perspicuity, this mode of classi- 

 fication will not, probably, be so often used as the four divi- 

 sions before adopted. Notwithstanding it is allowed that no 

 such distinctions as primary, secondary, and tertiary absolutely 

 exist in nature, and that there is no imperative necessity for 

 applying such terms, it is maintained that the system is ex- 

 tremely convenient and intelligible, and that it ought to be 

 continued ; at all events, that we are justified in using it until 

 some one can contrive a better. 



Without entering into a disquisition on the comparative 



