2G8 PEOFS. LLOYD MORGAN AND EEYKOLDS ON THE [Aug. IQOI, 



In the same part of the Transactions (p. 216) appeared Buckland 

 & Conybeare's classical ' Observations on the South-western Coal 

 District of England.' They stated that it had been their intention 

 to devote a chapter to the district immediately north of Tortworth ; 

 but owing to the presentation of Thomas Weaver's detailed paper, 

 they determined to suppress their own more rapid sketch. They 

 entered a protest, however, against Weaver's general conclusions. 



' Two masses of amygdaloidal trap,' said they, ' are found traversing the trans- 

 ition-limestone and the Old Eed Sandstone, which from their general parallelism 

 to one another and to the strata which bound them, might appear at first sio-ht 

 to be regular beds. We are of opinion, however, after a carefid examination of 

 their course, that they really are portions of dykes irregularly traversing the 

 other rocks. The thinness of these masses at their eastern extremity contrasted 

 with their thickness on the west towards Woodfoi-d Green, and more especially 

 the mode in which at the latter place they penetrate among and entangle frao-- 

 ments of the contiguous coralliferous limestone, which have been altered by the 

 contact; these are the circumstances which have induced us to form this opinion 

 concerning their nature.' (Ti-ans. Greol. Soc. ser. 2, vol. i, pt. ii, 1819, p. 248.) 



The statement here made, that the trap traverses the transition- 

 limestone and the Old Red Sandstone is erroneous. What- 

 ever be its mode of origin, the trap is certainly confined to the 

 Silurian. At Damery Eridge, however, it overlies a red shale with 

 abundant mica-fiakes. It is possible that this was mistaken by 

 Buckland & Conybeare for Old Red Sandstone. Rut the occurrence 

 of Lingula Symondsi, Salt, in these shales places their Llandovery 

 age beyond question. 



In his 'Silurian System' (1839), Murchison strongly advocated 

 the intrusive origin of the igneous rocks. On pp. 457-58 he 

 remarked that 



' The Tortworth trap-rocks whether viewed upon the natural surface, or in any 

 of the numerous quarries in which they have been laid open, consist almo.-st 

 exclusively of amorphous masses, of irregular shape and unequal thickness, 

 which protrude through and dislocate the overlying strata ; sometimes throwing 

 them off in discordant directions, at other times enveloping their fractured and 

 dismembered portions within the masses of the trap.' 



A description of the igneous rocks of the Tortworth district is 

 included in Phillips's Geological Survey Memoir (vol. ii, pt. i, 1848) 

 on ' The Malvern Hills compared with the Palaeozoic Districts of 

 Abberley, etc' On p. 194 he says : — 



'The manner in which the trap ... appears among the strata is of that kind 

 denoting irruption and partial interposition. About Charfield Green, and 

 in the line from Avening Green, through the wood, the trap shows for 

 certain distances a parallelism to the stratifications and a lamination of its 

 own substance corresponding thereto, but this is continually interrupted 

 by that irregularity of admixture, inter-ramification, and including of strati- 

 fied masses which always belong to irruption-trap. Successive flows of the 

 pyrogenous rock on different levels of the Caradoc [Llandovery] deposit, 

 with limited local disturbances, seem to be clearly indicated by all tlie facts 

 observable. The trap appears only in the midst of Caradoc [Llandovery] beds, 

 it is partially interstratified with them, follows their inclinations, and yet is 

 partially injected amongst them; it is, therefore, an irruptive trap, but of 

 what particular geological age we have some probable indications rather than 

 complete and certain proof.' 



