Mudie's Natural History of Birds, 357 



beds, as well as a deep fissure in the ash-coloured sand filled 

 with pebbles, &c. The whole mass consists of layers of sand 

 and pebbles, containing irregular traces of the ironshot and 

 greenish sands, and patches of the blue and brown clays, 

 having a considerable inclination to the east and north. 



Upon a general view, this pit affords two interesting facts : 

 first, a period of quiet deposition ; secondly, of more violent 

 action. 



During the first, the causes then in action must have been 

 favourable to the quiet deposition of the ash-coloured, green- 

 ish, and ochreous sands ; to the accumulation of the blue and 

 brown clays ; to the developement and existence of marine 

 animal life, as the O'strea, Cerithia, &c. To account for the 

 gradual mingling with these marine remains, the fluviatile 

 Testacea, we must infer, from the living habits of the recent 

 genera # , that they also inhabited tidal rivers and estuaries. 



To the second period belong the pebbles and sand contain- 

 ing the fragments of shells, as well as the irregular beds at 

 the north side of the pit : in this case, the various horizontal 

 strata seem to have been torn up by violent action, as well as 

 mixed with other detritus, and spread over the various sur- 

 faces in the neighbourhood. The inclination of this gravelly 

 debris towards the north may be observed in other places, as 

 in the lanes leading to Plumstead Common, Bexley Heath, 

 Erith, &c. 



Kensington, Jan, 14. 1835. 



[We thank the author for the expressive sketches which he 

 has sent us in illustration. The description supersedes these, 

 we think.] 



REVIEWS. 



Art. I. Titles of Works on Subjects of Natural History, published 



recently, 



Mudie, Robert, Author of " The British Naturalist," " Guide 

 to the Observation of Nature, &c.:" Natural History of 

 Birds. London, 1834, 4s. 6d, 

 Mr. Mudie, well known to every ornithologist as the author 



of the Feathered Tribes f, has produced a clear, compendious, 



* Cyrena, rivers of China ; Potamis, rivers of Africa, estuaries ; Mela- 

 nopsis, Danube, Levant. 



f The Feathered Tribes of the British Islands, by Mudie, 2 vols. 8vo, 

 1/. 8s., and the British Ornithology, by Selby, 2 vols. 8vo, 1/. 1*., are per- 

 fectly indispensable to every admirer and student of the birds of Britain : 



