MURCHISON'S SILURIAN RESEARCHES. 105 



§ 2. MURCHISON'S SILURIAN RESEARCHES. 



It is no new thing in geology, for rocks, where they conic together, to conform nearly 

 m dip and strike, though (hey may he of very different ages. A case in point is given in 

 the Silurian Researches, where the Coal measures conform so nearly in their strike with 

 the Cambrian rocks, that the unpractised geologist would he misled by appearances. I give 

 the passages entire, as they contain important matter. The first is introduced by stating 

 that the Salopian coal measures repose on rocks of all ages, from the Mountain limestone 

 to the Cambrian rocks inclusive. "This collocation," the author remarks, "which in 

 •• Shropshire cannot lead us into error, has been productive of confusion in those situations 

 ■• where the coal measures put on the lithological aspect of the older deposits, and at the 

 " same time rest directly upon them ; and if there is no striking want of conformity between 

 •• these masses, their separation becomes a subject of difficulty to persons not habituated 

 " to such phenomena." And he goes on to state, that at Nolton it would be difficult to 

 define the boundary between the culm beds and the lower Silurian shale and sandstone, in 

 consequence of the striking coincidence in the lithological aspect of the two rocks, and the 

 very little apparent discrepancy in their position. Another case alluded to, is one where 

 the Culm measures appear to pass downwards into Cambrian rocks ; at which place, view- 

 ing the cliffs from the shore, it is no easy matter to define where the older strata cease and 

 the younger begin. His conclusion is, "Now if this junction were not exposed in a bold 

 " sea cliff, where the faces of these rocks are completely laid bare, how much might have 

 " been written upon conformability and passage, and what erroneous inductions might have 

 " been drawn from these fallacious appearances !" It appears, therefore, that rocks as 

 new as the Coal measures have assumed the age and appearance of the Cambrian rocks, 

 and that they cannot he distinguished without the most careful observations, even where 

 there is the best possible exposure, that of a naked sea cliff. We need not be surprised, 

 then, that rocks still older should, occasionally at least, appear in the same condition as 

 those described by Mr. Murchison. 



VIII. MINERAL PRODUCTS OF THE TACONIC SYSTEM. 



Five important products are derived from the Taconic system: Brown hematitic iron, 

 black oxide of manganese, roofing slate, the white and clouded marbles, and limestone. 

 In addition to these, I might add ilagging stone, which is of some consequence in districts 

 not supplied with that material from the Hclderberg range. 



[Agricultural Report.] 14 



