626 Correspondence — Mr. C. Moore. 



the very regular columnar ranges, to which Mr. Mallet's theory- 

 relates, have, one and all, evidently cooled from the bottom ; the 

 upper portions of the basaltic beds being nearly amorphous, or, if 

 prismatic at all, composed of very imperfect groups of prisms. 



Apart, indeed, from Mr. Mallet's ideal columns, I will state, as 

 the result of my own observations, that in every natural section of 

 a basaltic columnar range, the plane separating the portion in which 

 cooling probably began below from that in which cooling began at 

 the upper surface, is, as a general rule, horizontal ; the two portions 

 being as distinct as is the architrave in a Greek temple from the 

 supporting columns (as may be seen in any good drawing of Staffa, 

 or of the basaltic columnar ranges of the Vivarais, Auvergne, etc.). 

 The upper portion is, indeed, generally amorphous, or nearly so, and 

 so decidedly separated from the lower regular columnar range, as to 

 have been usually mistaken for a separate lava-flow of later forma- 

 tion. If Mr. Mallet's notion could be realized anywhere, it would 

 be in the horizontal columns of a vertical dyke, formed by contem- 

 poraneous cooling from both of its sides. I will, however, venture 

 to say that no instance can be produced of a single continuous column 

 passing unbroken, from side to side, of any dyke. Can Mr. Mallet 

 produce any example of such a fact from his own observations? 

 The columns, on the contrary, always terminate towards the centre 

 of the dyke, either in a seam of amorphous lava, or an interval filled 

 with rubble (and this Mr. Mallet himself admits, as in the former 

 instance, p. 183), or sometimes they are separated by a still more 

 recent vein of lava. Finally, I leave it to all geologists interested 

 in the question, to examine the columns in the possession of their 

 Society, and form their own opinion upon the point in dispute be- 

 tween Mr. Mallet and myself. 



It is of the more importance from its having anlndirect bearing 

 on the main question as to the influence of concretion, no less than 

 of simple contraction, upon the production of the columns themselves : 

 a question upon which, likewise, I have the misfortune to differ with 

 Mr. R. Mallet, who will not admit of any concretionary action at all 

 — even, for example, in the case of the nearly globular articulations 

 of the prisms of the Cheese-Cellar at Bortrich. But upon this 

 point, I will not here enlarge. 



Cobham, November Zrd, 1875. G. PotTLETT Scrope. 



ON THE PEESENCE OF THE GENEEA PLICATOCRINTJS, COTTLE- 

 DERMA AND SOLANOCRINUS IN BRITISH STEATA. 



Sir, — At the British Association Meeting a few weeks since, F. 

 Longe, Esq., F.G-.S., of Cheltenham, handed to me a very perfect 

 example of the interesting but little known Crinoid Plicatocrinus which 

 had been found by him on the coast near Bridport. He informed me 

 he had shown it to Dr. Wright, who had referred it to the family 

 Cirripedia, to which at first sight it bears some resemblance. 



I explained to Mr. Longe that this was incorrect, as it belonged 

 to the Crinoidea, at which group Dr. Wright had so long been work- 

 ing, and that I was already possessed of several of the above genera 



