288 Correspondence — Dr. G. Linnarsson, 



to the various divisions of the Cambrian and Lower Silurian systems 

 are nothing but equivalents of the uppermost 1000 ft. of the British 

 Caradoc group. I think that Mr. Hicks himself will shrink from 

 such a conclusion. But, if the conclusion is false, there must be 

 some fault in his own reasoning, on which it is based. We must, 

 therefore, suppose that the depression took place far more slowly in 

 the Swedish area. I think that this must be so, because the Swedish 

 area was more oceanic and more remote from volcanic districts, 

 where it is natural that more sudden depressions take place. 



Second^, Mr. Hicks objects to my proposal to unite the Upper 

 Harlech beds with the Menevian group. As to this, I will not deny 

 that it may be convenient to separate them as local groups, but I 

 still hold the opinion that the difference, in palseontological respect, 

 between the Harlech and the Menevian group, is not comparable, 

 for instance, to that between the Menevian group and the Lingula 

 flags, or to that between the Lingula flags and the Tremadoc group. 

 If the term Menevian were to be transferred to other countries than 

 Britain, I think that it ought to have its range extended so as to 

 comprise all the strata of which Mr. Barrande has formed his Phases 

 a Faradoxides. 



As to Mr. Hicks' general assertion, in the beginning of the letter, 

 that the facts brought forward by me, far from invalidating any of 

 his views, tend strongly to confirm them, I look forward to the con- 

 tinuation of his paper in the Geological Mx^gaztne, where the 

 meaning of these words will probably be more fully explained. At 

 present, I must own that I cannot understand how, for instance, 

 the fact that the lowest Russian beds underlie a horizon which in 

 palseontological and stratigraphical respect corresponds to the British 

 Lower Tremadoc (or, according to the classification of Mr. Salter, to 

 the uppermost Lingula flags) can very strongly confirm Mr. Hicks' 

 opinion thas they are of Arenig age, nor liow the fineness of the 

 sediment in the Paradoxides and Olenus beds of Sweden can prove 

 them to be shore deposits as they ought to be, at least for a large 

 part, according to Mr. Hicks' views — not to refer to any more •• 

 examples. G. Linnarsson. 



Stockholm, Mai/ 15th, 1876. 



P.S. — Erratum. — There is an Erratum in my last communication which appeared 

 in the Geological Magazine for April last at p. 149, 20 lines from foot of page, 

 for " older than any metamorphic rocks of Scandinavia," etc., it should read " older 

 than any ?2ow-metamorphic or ' clastic' rocks, etc. — G.L. 



CoNCHOiDAL Fracture of Flint. — It may be interesting to notice 

 in connexion with this subject, alluded to in the Eeport of the 

 Geological Society of Stockholm, (see ante p. 281), that the late 

 Mr. C. B. Ptose, F.G.S., read a paper thereon at the Meeting of the 

 British Association at Norwich, 1868. The structure is well known 

 in the Chalk Flints of Norfolk, and is developed by hammering. 

 The " dressed " surfaces of old flint walls, Bishop's Palace Garden, 

 Norwich, show it admirably well. — Edit. Geol. Mag. 



