322 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



So that, in round numbers, considering that we nowhere reach the 

 upper limit of the Coal-measures, we may take the combined thick- 

 ness of the sedimentary materials at 19,000 feet as originally depo- 

 sited in this part of England. 



We have now to compare these measurements with others taken 

 at intervals along a south-easterly line, or along the direction of 

 attenuation, Leicestershire being the extreme point where the 

 comparison can be made in the case of the Carboniferous rocks. 

 The thickness in these cases are also taken from sections of the 

 Geological Survey — some measured by Mr. A. H. Green, some by 

 myseK *. 



Comparative vertical sections of the Carboniferous strata from 

 North Lancashire to Leicestershire. 

 N.N.W. _ S.S.E. 

 Burnley Mottram North Leicester- 

 district, district. Staffordshire. shire. 



Coal-measures 8460 7635 6000 3000 



Millstone-grit series . . 5500 2500 500 50 



Yoredale series 4675 2000 2300 50 



18635 12135 8800 3100 



From the above comparative sections it wiU be observed that the 

 beds which attained so prodigious a development in North Lanca- 

 shire dwindled down to one-sixth of their volume in Leicestershire, 

 in Central England, near which place the Mountain-limestone at- 

 tains a great but unknown thickness f. 



In fact, the development of these beds in Xorth Lancashire has 

 surpassed that of the contemporaneous beds of South Wales, hitherto 

 considered to present the largest vertical series of Carboniferous 

 sedimentary rocks in the British Isles ; and, as far as we know, it 

 is only exceeded in Europe $ by that of the Coal-field of Ehenish 

 Prussia, where the beds, according to the estimate of Herr von 

 Dechen, reach a thickness of over 20,000 feet. Turning to the 

 continent of America, and taking the series of Xova Scotia as re- 

 presenting the maximum accumulation of sedimentary beds, we find 

 that it is exceeded by that of jSTorth Lancashire, though, as Dr. Dawson 

 has shown, the section is incomplete, and scarcely presents a fair 

 point of comparison. 



Professor Phillips, in his ' Geology of Yorkshire,' observes, " the 

 thickness and purity of the argillaceous deposits being to the west, 



formable overlap of the Permian and Trias at Manchester, as shown by Mr. E. 

 W. Binney, F.R.S. See " Geology of the Country around Oldham and Man- 

 chester." 



* Messrs. Hull and Green " On the Millstone-grit of !N"orth Staffordshire," &c., 

 Qiiart. Journ. Geol. Soc. vol. xx. p. 242 et seq. 



t At least 4000 feet, according to sections which I levelled in the neighbour- 

 hood of Ashbourn. 



^ After reading the description in Sir E. Murchison's work on the Geology 

 of Russia, I was under the impression that the beds in the coal-field of the 

 Donetz attain a greater vertical thickness; but, from some statements by Sir 

 Roderick himself. I found my opinion was incorrect. 



