570 Geological Society, 



Before he proceeds to detail his own observations, Mr. Weaver 

 gives a comparative table of the subdivisions of the strata, exhibited 

 by Prof. Sedgwick and Mr. Murchison at the meeting of the British 

 Association at Bristol, in August 1836 ; and those employed by the 

 Rev. David Williams, in a section shown at the meeting of the 

 same body at Liverpool, in September 1837. These subdivisions, he 

 states, are essentially the same, though Mr. Williams considers the 

 coal strata as belonging to the transition systems. 



The subdivisions, first established at the Bristol meeting, are 

 adopted by Mr. Weaver, but he employs a nomenclature derived, for 

 the greater part, from the localities where the strata are well exhi- 

 bited. The following list contains the subdivisions in ascending 

 order. 



1. Foreland sandstone. 2. Linton calcareous slates. 3. Tren- 

 tishoe quartzy slates and sandstone, including the Combe Martina 

 limestone. 4. Morte slates. 5. WoUacomb sandstones, flagstones, 

 and slates. 6. Trilobite slates. 7. Wavellite schistus and lime- 

 stone. 8. Culmiferous shales (coal strata). 



The mineral composition, lithological structure, local variations, 

 and relative order of superposition of each formation are fully detailed ; 

 and the following inferences are given, as deducible from the whole 

 of the evidence, collected during the survey. 



'Iliat there is a general sequence of emergence from south to 

 north, or from the culmiferous shales (8) to the Foreland sandstones 

 (1), the dip being generally to the south. 



That from the Foreland sandstones (1) on the north to the 

 Trilobite slates (6) on the south inclusive, the angle of dip increases 

 from 20° to 80°, being 20° to 30° in the Foreland sandstones (1) and 

 Linton calcareous slates (2), 45° to 70° in the Trentishoe quartzy 

 slates and sandstone (3), 70° to 80° in the Morte slates (4) and 

 WoUacomb sandstones (5), and generally in the Trilobite slates (6), 

 though in the last a lower angle is sometimes observable on approach- 

 ing an undulation. The general strike of the beds is from 10° to 15° 

 N. of W. and S. of E. from a true meridian. 



ITiat on the other hand the Wavellite schistus, limestone, and 

 shale (7) and culmiferous beds (8) undulate on a very large scale, 

 and are occasionally subject to contortions upon a smaller. 



From the Foreland sandstones (1) to the Trilobite slates (6) in- 

 clusive, the series is connected throughout, passing from one to the 

 other in such a manner as to form a consistent whole, the parts of 

 which cannot be separated one from another without arbitrary divi- 

 sions. 



lliough the beds, from 1 to 6 inclusive, form one consistent, 

 consecutive series, yet the subordinate parts are subject to change in 

 different portions of the field, both mineralogically and in extent, 

 and occasionally thin out, as in the case of the beds of limestone. 



On the other hand, the Wavellite schistus and limestone (7) 

 and culmiferous shales (8), though apparently in some places in a 

 parallel (conformable) position with the Trilobite slates (6), do, 

 when thoroughly examined upon the line of outcrop in the district, 

 form a break with number 6, and are unconformable thereto. 



