254 Geological Systems — Geological Maps,fyc. 



and structure, which proves the extension and similarity ©f 

 their formation. 



The secondary and alluvial, consisting of the wreck of more 

 ancient rocks, vary with the locality and nature of the rocks 

 from which they originate, and have nothing fixed or general- 

 ly characteristic of a universal formation Depending on the 

 accidents of declivity, he, of the foundation on which they 

 are placed, without any regular direction of the stratification, 

 each basin has its own relative position ; and as they touch 

 each other at the sides, they are not subject to any over-lying 

 stratification that can fix the relative period of their dififerent 

 formation. 



Smith, in his Geological Map of England, (if I recollect 

 well, for I have not seen it for many years,) places the secon- 

 dary of the west on the primitive and transition of the Cum- 

 berland mountains, and in the section which he gives, all the 

 secondary of the east overlies them, by which he indicates, 

 that all the chalk of the east overlies the coal of the west : an 

 order on which others have built their theories, and which I 

 rather thiuK is not correct. The Vulcanic class is a little 

 more irregular. It certainly alternates with the alluvial and 

 secondary, and I think with the transition, so that its formation 

 has been coeval with the three Neptunian classes. 



Perhaps the most useful classification, in the present state 

 of the science, would be to retain Werner's five classes as 

 being well defined, that is, as well as the graduated variety of 

 nature will permit, (for one spec-es runs into anoth( r by such 

 small and imperceptible degrees as scarcely to leave a footing 

 for our artificial divisions) and to make some subdivisions in 

 each class, without deranging the system already best known, 

 or the ideas of those who follow it. Werner, in placing his 

 newest Floetz Trap in the secondary class, commits a great 

 fault, for these rocks alternate with the alluvial secondary and 

 most probably even with the transition, and are mostly an- 

 cient Vulcanic rocks. It is probable that the secondary is 

 the most defective class in his system, for like all system- 

 makers he copied what he saw, and the Erzgebirge, the 

 field that produced his system, has little or no secondary, but 

 with the exception of the newest Floetz Trap it is the most 

 natural and least complicated or confused geological forma- 

 tion I have yet seen. To collect facts, without being warp- 

 ed by an attachment to system, is the surest mode of advanc- 

 ing geology, as well as all other sciences^ and it gives me 



