SECONDARY ROCKS— GENERAL RELATIONS. 19 



to justify the misconceptions of some who have examined it.* 

 The mountain limestone, which, if it preserved that position 

 which it is generally found to occupy in other districts, 

 would be a formation separating the white from the red sand- 

 stone series, occurs in the Lothians connected with both. 

 While making these statements indicating that the causes 

 which produced the Secondary formations of the Lothians 

 were uninterrupted during the deposition of the series, and 

 that this circumstance accounts for the various alternations 

 of its members, we may remark, that there has been a source 

 of error in the belief, that in all instances three distinct de- 

 posits,-]- viz., the Old Red Sandstone, the Mountain Lime- 



* Dr Hibbert, in his paper " On the Limestone of Burdiehouse," publish- 

 ed in the Transactions of the Royal Society of Edinburgh, vol. xiii., 

 page 137, affirms, that, by ignigenous action, " there has been an emer- 

 gence of beds even inferior to the carboniferous group," and cites the 

 Pentlands and the coast of North Berwick as localities. The strata ex- 

 posed there, however, are all of the same general nature as the red sand- 

 stones of other places, which, by their relations to the white sandstones, 

 so clearly indicate that both series constitute one contemporaneous 

 formation. The red sandstone of Hawthorkden, exhibited also to Dr H. 

 some appearances which caused this observer to believe that it had 

 been deposited soon after the formation of the Transition rocks. In re- 

 gard to what these were we are ignorant ; but if viewed in all its relations, 

 it will be found to form only one of those deposits of red sandstone, 

 which, with those of white sandstone, coal, and shale, form the second- 

 ary system of the Lothians, and geognostically represent the coal forma- 

 tion. 



t As an instance of this we may mention the conclusions to which 

 Messrs Sedgwick and Murchison came, after examining the secondary 

 formations of the island of Arran. In that island two red sandstones oc- 

 cur, the one above, the other below, the strata of white sandstone con- 

 taining beds of coal, while the Mountain Limestone occurs interstratified 

 with both. After examining this district, these geologists were led to 

 consider that series of red sandstone strata, which was in the more im- 

 mediate vicinity of the old rocks, as the Scottish representative of the 

 old red sandstone of England : the assemblage of white sandstone was by 

 them described as the Coal formation ; while the red sandstone which lay 

 above it, was stated to be the equivalent of the new red sandstone of 

 England, differing from it, however, in this circumstance, that in Arran 

 it was conformable with the coal formation. By 



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