PREVAILING VIEWS AS TO CONDITION OF ORIGIN 351 



area and depth. These would dry out until the next period of rains filled 

 them." 



"We attain therefore the conception that the northern continent, already in 

 the Upper Cambrian, again in the Upper Silurian, and further through the 

 whole of the Devonian period, even into the Lower Carboniferous, possessed a 

 hot desert climate whose dry periods were broken only seldom by the down- 

 pours of thunder-storms." 



AValther considers the red colors as original to the sediments. From 

 this he derives his name of the Old Eed Northland. There has been pre- 

 sented, however, no evidence that the original sediments had the present 

 color tones of the solid rocks. Dehydration and change in color of the 

 iron oxide commonly accompany thorough cementation. Neither has there 

 been presented evidence of pronounced wind action or the existence of 

 evaporation deposits. It seems, therefore, that this picture of a desert 

 climate is overdrawn. A truer view may center on a semi-arid climate 

 and a land whose character lies half way between the permanent lakes of 

 the British geologists and the permanent deserts of Walther. 



Jukes-Browne published in 1911 a revision of his volume on "The 

 Building of the British Isles." In the chapter on the Devonian period 

 he discusses the evidence which goes to show that the basins of Old Eed 

 deposition were originally much wider than their present limits. The 

 small areas he regards as remnants isolated by erosion. The difference 

 in the faunas and floras of the Caledonian and Orcadian areas must 

 therefore, as Traquair has argued, be due to shifting of subsidence and 

 consequent shifting of deposition during the course of the Devonian, and 

 not to the maintenance of permanent mountain barriers between them. 

 Jukes-Browne recognizes Goodchild's arguments for a climate at times 

 desert in character, but refers to the areas of deposition as lakes. These 

 lakes, under his conception of greater area of deposit, become in fact 

 fresh-water seas of far-reaching extent- Thus the essentially lacustrine 

 conception is maintained and fluviatile deposition is not accorded a place 

 of importance. 



In -America the trend of opinion in regard to the proper interpretation 

 of the Old Bed Sandstone has been increasingly in the direction of ascrib- 

 ing a larger importance to fluviatile deposition, but these views are mostly 

 unpublished and have naturally therefore carried no weight in British 

 opinion. The earliest American expression of view, in what is here re- 

 garded as the right direction, was, so far as the writer is aware, that by 

 T. C. Chamberlin in 1900. This pioneer in geologic thought, in a paper 

 of philosophic nature on the habitat of the early vertebrates, suggested 

 that the Old Bed Sandstone was deposited under conditions not unlike 



XXVI — Bull. Geol. Soc. Am., Vol. 27, 1915 



