Mr. Bakewell on the Coalfield near Manchester. 285 



Yorkshire. There Is, generally speaking, a considerable difference 

 in the external characters of these two beds ; but at Alderley edge* 

 some parts of the red rock, containing mica, bear a greater resem- 

 blance to the shale than I have found in any other situation where 

 I have examined it. 



, Mr. Whitehurst observed that a species of grit-stone, which he 

 denominates the Mill-stone grit, is found under the coal, but never 

 over it. This bed of rock, which in some situations is not less than 

 140yards in thickness, varies in quality from a coarse-grained grit, 

 approaching to a breccia, to a fine-grained siliceous sandstone. Some 

 varieties of it are red, and bear a greater resemblance to the sand- 

 rock of Lancashire and Cheshire than the red shale, which lies be- 

 neath the mill-stone grit. 



It is not improbable that in distant places the same stratum may 

 assume different characters, particularly when it belongs to that class 

 of rocks which have been considered by geologists as mechanically 

 deposited by the action of the tides. Strata thus formed may reason- 

 ably be supposed to alter with the materials of which they were 

 made ; materials that have been washed from the different parts of 

 extensive ranges of mountains variously composed. I am not aware 

 that this view of the subject has before been taken by geologists, 

 although we may thus account for the gradual transition of rocks 

 into one another, and may often give a more natural solution of the 

 sudden changes we observe, than by the supposition of faults, of 

 whose existence some evidence should always be given. Independent 

 of the difficulties which their admission would explain. 



In thus comparing the geognostic position of the Red sandstone 

 with that of the Mill-stone grit, I do not wish to advance any 

 opinion of my own as to their identity, but merely to direct the 

 attention of future enquirers to this subject. 



* For the account of Cobalt ore contained in the lied rock a( this place vide Monthly 

 Magazine, February, 1811, 



