178 Reviews — Geological Survey of England and Wales. 



and Arctic Foxes, both young and adult, are not rare, but much 

 scattered. Eemains of Equus, Arvicola ratticeps, A. amphibia (or 

 My odes Obensis), Lagomys sp., Lepus sp., Spermophilus sp., and of a 

 species of Bat, seem to exclusively belong to the upper portion. The 

 loam of this horizon contains a notable proportion of sand, and is 

 divided into distinct horizontal strata, two to three centimetres thick, 

 layers with coarse-grained sand generally alternating with beds either 

 containing fine-grained sand, or quite loamy. Here and there large 

 pebbles, up to the weight of 200 grammes, are found, but not so 

 large nor so abundant as in the " Mammoth horizon." The pro- 

 portion of lime is rather considerable, and calcareous concretions are 

 not of rare occurrence, especially in connexion with the fossil bones. 

 III. Conclusions. — The ossiferous deposits of Thiede are essentially 

 the result of violent currents of flood-waters. During the intervals 

 between two inundations, winds, more frequent in the dry summer 

 months, may have brought a considerable amount of sand and dust 

 over this the exposed region, depositing these substances among the 

 gypsum cliffs of Thiede. The effects of atmospheric currents are 

 chiefly conspicuous in the upper horizon, less distinct in the lower- 

 most, and not at all perceivable in the middle horizon. This assertion 

 is proved, first, by their high level above the present level of the 

 nearest river ; secondly, by their petrographical constitution ; thirdly, 

 by their organic remains belonging nearly all to land-animals, and 

 mostly to forms proper to Steppes, which are continually subject 

 to subaerial accumulations of sand and dust, such as Von Eichthofen 

 has observed on a very large scale in the undrained Steppe-regions of 

 Central Asia. The few traces of water-action may be explained by 

 local inundations, in consequence of occasional heavy rains. If we 

 suppose the " Lemming deposits " of Thiede to belong to the Glacial 

 (and, if we admit two such periods, to the Second Glacial period), 

 the middle and upper horizons at Thiede, as also the whole of the 

 deposits at Westeregeln, should be ranked among those of the Post- 

 glacial period, when Western and Central Europe had taken a more 

 continental form, and certain regions were subjected to a dry Steppe- 

 climate. 



EEYIE "W S. 



I. — The Geological Survey of England and Wales. 



The Geology of the N.W. Part of Essex, and the N,E. Part 

 of Herts, with Parts of Cambridgeshire and Suffolk. [Ex- 

 planation of Sheet 47 of the Geological Survey Map of England 

 and Wales.] By W. Whitaker, W. H. Penning, W. H. Dalton, 

 and F. J. Bennett. 8vo. pp. 92. (London, 1878.) 



THE Geological Survey is gradually extending its labours over 

 the northern and eastern counties ; and there now remains not 

 an English county which has not been partially surveyed, nor one 

 of which some account has not been published " by order of the 

 Lords Commissioners of Her Majesty's Treasury." 



