Geological Observations. 183 



I BELIEVE it is an opinion with many, that the limestone which 

 so constantly incloses the coal-fields in England belongs to the 

 transition series. This opinion is most distinctly stated in a re- 

 cent publication by Dr. Kidd, who has at some length endeavoured 

 to show the correspondence of the gray mountain limestone of 

 Somersetshire, and elsewhere, with the transition limestone of the 

 Wernerian arrangement. Tiiis opinion appears to me to be very 

 erroneous; for, in the country which I have described, there are, 

 1 think, sufficient grounds for referring it to the first floetz series. 

 In geological examinations it frequently happens that individual 

 rocks are so indifferently characterized, "that it is impossible, with- 

 out attending to tho formations with which they may be accom- 

 panied, to refer them to their true position in a systematic ar- 

 rangement. When a rock, as limestone, occurs in all the gratKl 

 divisions of a system, it is most hopeless, without such correla- 

 tive evidence, to guess at its true geological rank; for limestone, 

 whetlier from a j)rimitive transition or a floetz country, must 

 still be carbonate of lime ; and it is hardly to be expected that 

 the same substance should assume characters decisive of the 

 class to which it belongs. Thus the primitive or granular 

 limestone, which is well characterized by its highly crystalline 

 fracture, sometimes occurs among floetz and transition strata; but 

 no geologist, in seeing the granular limestone i?i situ with mica 

 slate or gneiss, would hesitate in calling it primitive ; for these 

 rocks never occur among those of the floetz or transition de- 

 Rcription. In the same manner, no one upon seeing limestone 

 associated with gray wacke, would doubt as to its being transi- 

 tion, for gray wacke is a rock exclusively of transition formation. 

 Provided therefore om- system be correct, however puzzling it 

 may be by external characters alone to refer any rock, common 

 to all the divisions of the system, to its true position, by attending 

 to its geological relations we soon find a solution of our diffi- 

 culties. I have made these remarks, because Dr. Kidd, in con- 

 •sidering the mountain limestone to be transition, has been a 

 good deal guided by its sometimes (though never where I have 

 seen it) agreeing, as to its external characters, with those which 

 Mr. Jameson has ascribed to transition limestone, while he has 

 completely misunderstood or overlooked its relation with other 

 rocks. 



it will be seen, by referring to my Description of the Neigh- 

 bourhood of Bristol, that the mountain limestone rests upon a 

 red sandstone. I have only, indeed, mentioned two places where 

 this connexion can be observed; but this I am persuaded is 

 owing to the sandstone occupying the champaign and cultivated 

 parts of the country, so that it is difficult to ascertain its existence 

 iiniX relation with the limestone, excepting where the stratifica- 

 M 4 tion 



