vi The Transition Rocks or Greywacke 245 



their sequence in the same orderly manner as had led to 

 the recognition of the succession of the younger formations. 



It will be remembered that in his original scheme of 

 classification Werner grouped some rocks as Primitive 

 (uranfdngliche), and classed together as Floetz the whole 

 series of stratified formations between these and the 

 alluvial deposits. Further experience led him to separate 

 an intermediate group between the Primitive and the 

 Floetz, which he denominated Transition. He believed 

 that this group was " deposited during the passage or 

 transition of the earth from its chaotic to its habitable 

 state." 1 He recognized that it contains the earliest 

 organic remains, and believed it to include the oldest 

 mechanical deposits. He subdivided the Transition 

 rocks rather by mineral characters than by ascertained 

 stratigraphical sequence. The hardened variety of sand- 

 stone called greywacke formed by far the most important 

 member of the whole series, and was believed by "Werner 

 to mark a new geognostic period when, instead of chemical 

 precipitates, mechanical accumulations began to appear. 



The two Wernerian terms Transition and Greywacke 

 survived for some years after the commencement of the 

 great stratigraphical revival in the early years of the 

 present century. They formed a kind of convenient limbo 

 or No-man's Land, into which any group of rocks might be 

 thrown which obstinately refused to reveal its relations 

 with the rest of the terrestrial crust. Down to the base 

 of the Carboniferous rocks, or even to the bottom of the Old 

 Eed Sandstone, the chronological succession of geological 

 history seemed tolerably clear. But beneath and beyond 



1 Jameson's Geognosy, p. 145 (1808). 



