Reviews — Action of Rain-water on Superficial Deposits. 279 



Amphibians and Eeptiles, a sound induction which must long have 

 been making its way with philosophical naturalists. 



It is impossible to conclude this brief notice without congratulat- 

 ing the author on the admirable way in which the memoir is pro- 

 gressing. It is indeed a model of monographic work, wrought out 

 of materials that would have discouraged if they did not baffle a 

 writer less patient, able and painstaking than Dr. Fritsch, and may 

 well call out the sympathy and admiration of his fellow-labourers 

 among: fossil vertebrates. H. G. Seeley. 



II. MeMOIRB SUR LES PHENOMENES d'alTERA-TION DBS DEPOTS 



SUPEHFIOIELS PAR l'iNFILTRATION DES EAUX METEORIQUES ETUDIES 

 DANS LEURS RAPPORTS AVEC LA GEOLOGIE STRATIGRAPHIQUE. Par 



Ernest Van den Broeck. 4to. pp. 180. One Coloured folding 

 Plate, and 34 figures in the text. (Brussels, 1881.) 



ri^HIS handsome Memoir forms part of vol. xliv. of the quarto 

 X series published by the Eoyal Academy of Sciences of Belgium 

 under the title of " Memoir es couronnes et Memoires des savants 

 etrangers.'" In it Mr. Vanden Broeck, who is well known as one of 

 the most zealous and active of the younger naturalists and geologists 

 of his country, has brought together a great number of facts relating 

 to the alteration of superficial deposits by the action of rain-water. 

 This subject was first taken up by the author in 1874, and since 

 that time he has taken every opportunity, by means of papers 

 describing special cases exhibited in various portions of the Tertiary 

 basin of the Netherlands, of calling the attention of geologists to 

 the frequent misreading of sections, due to the want of care in 

 distinguishing the altered, but undisturbed, parts of beds or groups 

 of beds from unconformable deposits. One of the first cases of the 

 kind, clearly explained by him, related to the Laekenian and 

 Bruxellian of the Brussels Eocene. Here unfossiliferous sands, 

 resting upon what had been generally regarded as strongly eroded 

 surfaces of fossiliferous more or less calcareous rock, were shown 

 to be really undisturbed portions of the latter, from which the 

 carbonate of lime had been removed, and in which other changes, 

 such as the oxidation of glauconite for instance, had taken place, by 

 the action of rain-water." This is a fair sample of the kind of 

 useful application that can be made for stratigraphical purposes of 

 a proper knowledge of the results of the long-continued percolation 

 of carbonated waters through sand and other deposits. Of course 

 these efiects have long been known to chemists and geologists, but 

 their application towards the lanra veiling of the often obscure details 

 of Tertiary geology is very largely, if not altogether, due to Mr. 

 Vanden Broeck. 



In the present Memoir, after some general considerations respect- 

 ing the role of water, and especially rain-water, as an agent in the 

 metamorphosis of rocks, the author describes its special action on 

 felspathic, metalliferous, clayey and shaley, siliceous, and calcareous 



^ See Annates de la Societe geologique du Nord, t. iii. p. 174. 



