80 EIGHTH REPORT— 1838. 



above. The memoir includes also a description of the Pottery coal- 

 field, which fills a long trough from Biddulph to Lane End, on a syn- 

 clinal axis from north to south. 



After a minute examination of many cases of disturbed stratification, 

 the author states that, upon the most general view of the position of the 

 carboniferous system, in this district, it is perceived to be one great 

 arched elevation on an axis from north to south, having also a gradual 

 slope to the south. This great elevation is made up of many minor 

 undulations, the higher parts of the middle of the arch being stripped 

 oiF, and the inferior beds exposed to view. On every side, as soon as 

 the beds descend to a sufficiently low level, they are masked from fur- 

 ther observation by beds of the new red sandstone. 



Mr. Jukes describes minutely the proofs of the gradual attenuation 

 of the magnesian limestone in its course to the South near Nottingham, 

 till it dwindles to one yard in thickness, and is lost under the westward 

 range of red and white sandstone which borders the Nottinghamshire 

 and Derbyshire coal-field on its south side. 



Connected with this supei-position of the red sandstones on coal, 

 (themselves covered by the red and white clays which constitute the 

 upper part of the red formation) is a point of great practical import- 

 ance, viz. the extent to which coal may be reasonably looked for be- 

 neath these red rocks. 



Among other evidence bearing on this question Mr. Jukes describes 

 the narrow extensions and peculiar aspect of the red sandstone in the vi- 

 cinitj' of Ashbourne ; notices the physical configuration of the country 

 along the junction line of the red formation and the coal strata, which 

 in places indicates a great depression of the latter, and the production 

 of valleys in it anterior to the deposition of new red sandstone. He 

 states, finally, that it is probable that a large part of South Derbyshire 

 and the adjacent district is composed of the rocks belonging to the 

 lower part of the carboniferous system, covered by the new red sand- 

 stone ; that the north point of the Leicestershire coal-field must be 

 looked upon as the connecting link between the coal-fields of Derby- 

 shire on the one hand, and of the north of Staffordshire on the other ; 

 that the present break between them was caused in pai"t by denuding 

 forces acting before the new red sandstone period ; and, consequently, 

 that any mining operations in the south of Derbyshire in search of coal 

 are unlikely to be attended with success. 



On the Silurian Si/sfem of Strata. By R. L MuRCiiisoy, 

 F.R.S., G.S., &IC. 



Mr. Murchison exhibited to the Section the finished geological map, 

 plates, and sections, prepared in illustration of his work on the Silurian 

 System, and described the principles on which the map and the other 

 illustrations were constructed and coloured. He also noticed the pro- 

 bable extent of this system of strata in the British Islands, on the con- 

 tinent of Europe, and other foreign localities. 



