92 



has proved the existence of an eruptive w^all of basalt which cuts oft' 

 the coal of the Treen pits, precisely in the linear direction of that 

 which has been called the Jewstone (basaltic) fault. The coal in the 

 proximity of the basalt is much altered and of no value. 



Wenlock and Coalbrook Dale. — The greenstones and amygdaloids 

 which rise up at various points through the carboniferous limestone 

 and coal measures of this tract, are marked by the author on the 

 Ordnance map, but he suggests that their chief interest will be ap- 

 parent when the survey of all the dislocations of these coal fields by 

 Mr. Prestwich, shall have been completed. 



Kinlet. — This is rather a peculiar trap, being a greenstone in which 

 white spots of granular felspar are dotted through a base of dark 

 liornblende. It rises into knolls, protruding through the coal 

 measures, flanked by old red sandstone. 



A^-ley and Sliatterford, — This dyke of trap has been described 

 by the Rev. J. Yates*, to which account the author adds some de- 

 tails respecting its structure, and the beds of coal, sandstone and 

 shale upon its sides ; the chief additional fact being, that the red 

 sandstone which immediately surrounds this narrow zone of coal 

 measures is not the new red sandstone of Bewdley and Kiddermin- 

 ster as formerly supposed, but a girdle of old red sandstone, with 

 beds of cornstone, which is distinctly separated from the new red 

 sandstone and folds round this peninsulated carboniferous tract. 



Conclusion. — From the natural phenomena described in the pre- 

 ceding pages it appears, 



1. That volcanic agency satisfactorily accounts for the appear- 

 ance of all the varieties of trap rock which are associated with the 

 grauwacke series, the old red sandstone, and carboniferous strata 

 in the country under review. 



2. That from the imperceptible passages which take place be- 

 tween the different varieties of these trap rocks it is difficult, from 

 mere lithological characters, to assign a separate age to each. 



3. That as some of the porphyritic and felspathic rocks, alter- 

 nate conformably with strata of marine origin containing organic 

 remains of a very early period, and as some of the layers in which 

 such remains are imbedded have a base of true volcanic matter, the 

 date of the origin of this class of rock is thereby fixed. 



4. That these conformable alternations of trap and marine sedi- 

 ment establish a direct analogy between their mode of production 

 and those replications of volcanic ejections and marine deposit 

 which are now going on beneath the present seas ; whilst they fur- 

 ther explain the manner by which, in times of the highest geological 

 antiquity, the porphyry slates were arranged in parallel laminae with 

 the sedimentary accumulations of that age. 



5. That the existence of certain strata containing organic re- 

 mains, yet possessing a matrix, composed in great measure of the 

 same materials as the adjacent ridges of trap rock, has strengthened 

 the inference that some of the ebullitions of these submarine vol- 

 canos were contemporaneous with the period in which these ani- 



* Geol. Trans., New Series, vol. ii. p. 249. 



