BUFFALO SOCIETY OF NATURAL SCIENCES 1 77 



dian time says: "There is evidence that, during the time when the 

 Orcadian Old Red was in course of being deposited, normal pluvial 

 conditions obtained for a time. The deposition of ferric oxide in 

 the old area of inland drainage ceased, chiefly in consequence of the 

 large quantities of vegetable matter which were swept into the old 

 lakes. This latter, in its turn, decomposed the solutions of sulphate 

 of lime, and liberated the calcareous matter, which in a state of 

 diffusion, or aggregated into nodules, now forms so conspicuous an 

 element in the Orcadian Rocks. Furthermore, the sulphate of lime, 

 in its turn, converted the vegetable matter into the bituminoids, 

 which, in a diffused form, permeated — one might almost say satu- 

 rated — so much of the Caithness Flagstones. I hold, therefore, that 

 the exceptional durability of the Caithness flagstones, which of course 

 is due to the large percentage of bituminous matter they contain, is 

 due to the fact that conditions of inland drainage, one of the phases 

 of desert conditions, prevailed where these occur during the Devonian 

 Period" (80, 220). 



Theories of Deposition. From data of the type just given, 

 three theories have been evolved, each based upon practically the 

 same observations in the field, but each involving very different 

 interpretations. . The oldest and most widely accepted explanation 

 for the Old Red sandstone is that it is a series of lake deposits; the 

 second theory, which quite rightly has never received very much 

 attention, is that of marine deposition; the newest hypothesis is that 

 the Old Red is dominantly of fluviatile origin and that the deposits 

 were not laid down in any permanent body of standing water, either 

 marine or fresh, but largely on the dry land as torrential and flood- 

 plain deposits or in evanescent playas. I shall briefly consider the 

 first two theories and the objections thereto, and shall then give the 

 third and some of the evidence favoring it. All geologists are agreed 

 that the sediments are clastic, that they were not deposited in the 

 deep sea, that they are land-derived and river-transported; the only 

 point of difference that has arisen is in regard to the locus of 

 deposition. 



Deposition in Lakes. This theory has been most fuJly expounded 

 by Geikie and has been generally accepted in the form in which he 

 gave it. For the British area he recognized five lakes on the basis 

 of the present outcrops, considering that the heavy conglomerates 

 marked the rocky lake shores of Devonic time, while finer deposits 

 pointed out the central portions of the lakes. The presence of desic- 



