Reviews — A. M. Levy — On Eruptive Rocks. 89 



or Parhinsoni -zone was connected also with the Cotteswold area. 

 He believes that a barrier was raised "after the deposition of the 

 Lower Lias and just before that of the Cotteswold Sands," and that 

 this barrier, for a time, disconnected the Bath and Cotteswold area 

 of deposit from that of Dundry and the Dorset area. From the 

 evidence brought forward this may be taken as an interesting and 

 important suggestion made to explain certain palaeontological 

 differences between the strata in the respective areas. 



Mr. Lucy contributes " Remarks on the Dapple Bed of the 

 Inferior Oolite at the Horsepools, and on some Pebbles from the 

 Great Oolite at Minchinhampton." The Dapple bed is the quarry- 

 men's name for a layer of Oolite that contains tiny quartz pebbles, 

 and also pebbles of Oolite distinguished from the matrix by a 

 difference in colour and texture. These latter, as Mr. Lucy remarks, 

 evidence " the destruction of older rocks of the same nature during, 

 or previous to, the deposition of the existing Oolite ;" while the 

 quartz pebbles he considers to have been derived from the Forest of 

 Dean. The pebbles said to have been obtained from the Great 

 Oolite had, in Mr. Lucy's opinion, been derived from the Drift, but 

 had dropped down a fissure in the Oolite. 



The Rev. H. H. Winwood furnishes "Notes on a Geological 

 Section between Tytherington and Thornbury." A very neatly- 

 drawn coloured section accompanies the paper ; and it may be 

 mentioned that this differs in some minor particulars from the 

 section published by Prof. Lloyd Morgan (Proc. Bristol Nat. Soc. 

 vol. vi. part i.). The section depicts the cuttings on a new line of 

 railway, and shows the Old Red Sandstone passing upwards through 

 the Lower Limestone Shales into the Carboniferous Limestone. 

 Full details of the strata are given by Mr. Winwood. At one point 

 a reversed fault brings fine-grained beds of Dolomitic Conglomei-ate 

 (like Magnesian Limestone), beneath the Carboniferous Limestone. 

 Other sections show Dolomitic Conglomerate, Keuper Marl and 

 Sandstone ; and altogether the making of the railway has furnished 

 a very instructive series of cuttings. H.B.W. 



III. — Structures et Classification des Roches Eruptives. 

 Par A. Michel Levy. pp. 95. (Paris, 1889.) 



THIS is primarily a spirited attack on the principles laid down 

 by Rosenbusch in his Mikroskopisehe Phjsiographie der massigen 

 Gesteine, and a revindication of those already set forth by the author 

 in conjunction with Fouque. Though perhaps stronger on the 

 critical than on the constructive side, this little volume is full of 

 fertile suggestions, and is certainly the clearest exposition of the 

 views of the French school which has yet appeared. 



The author maintains that the plutonic (granitoide) rocks, no less 

 than the volcanic and porphyritic (trachytoide), present evidence of 

 two distinct periods of crystallization, the products of which may 

 be easily discriminated ; but that in the former class the minerals 

 of the two periods have similar characters, while in the latter they 

 are dissimilar. To account for the complex structures of the acid 



