P. Maenair 8f J. Rcid—On the Old Red of Scotland. 115 



in the shape of marine deposits, for immediately resting upon this 

 ancient plain, wherever it has been preserved, we have the great 

 basal conglomerates of the Old Red Sandstone, which they all agree 

 in referring to a lake or fresh- water origin. 



The amount of misconception that exists as to the succession of 

 events after the plication of these early Palaeozoic rocks is indeed 

 wonderful, and may be traced principally to these theories of the 

 physical and geological development of our country given in 

 Sir A. Geikie's " Scenery of Scotland," the following being a very 

 fair example. Prof. Davis, 1 of Harvard University, in a paper on the 

 rivers of England contributed recently to the Royal Geographical 

 Society's Magazine, speaking of the marine plain of denudation, 

 as described in the aforementioned work, says : " Although perhaps 

 not absolutely stated, it is clearly implied that it was Devonian 

 erosion by which the once low and comparatively even surface of 

 the now uplifted and dissected Highlands was produced ; it is 

 plainly manifest that Devonian erosion consumed a great volume of 

 the contorted and overthrust rocks of the Highlands : witness the 

 great volume of the Devonian strata lying unconformably upon the 

 Highland rocks, and the identity of the Devonian conglomerate 

 pebbles with the rocks of the older teri'anes. It may indeed be well 

 argued from Sir A. Geikie's essay on the Old Red Sandstone of 

 Western Europe that a vast denudation was accomplished in earlier 

 times than the Old Red Sandstone period, and that by the close of 

 that period the Highland region must have been truly a diminished 

 lowland, a peneplain of small area and moderate relief." This is 

 a very good example of the misconception and general indefiniteness 

 which accompany Sir A. Geikie's description of the physical events 

 following the plication of the crystalline rocks of the Highlands, for 

 Prof. Davis speaks of Devonian seas having cut down the Highlands 

 to their base-level, and of conglomerates belonging to that age 

 resting upon them, and then of Old Red Sandstone conglomerates, as 

 if there were two distinct sets of rocks in Scotland, one marine and 

 Devonian, the other fresh-water and of Old Red Sandstone age. Of 

 course the error is quite excusable in one who has never studied the 

 rocks of our country, but only read of them in the " Scenery of 

 Scotland." 



IV. Petrological, and Other Considerations. 



We have already noticed the strong similarity between the con- 

 glomerates of the Torridon Sandstones and those of the later Old 

 Red Sandstone rocks. Both of them show evidence of glaciation, 

 and, as has recently occurred to us, this may be connected in some 

 way with the fact that they are both seen to follow a great process 

 of mountain-building. This fact, we think, would indicate that the 

 great mountain mass had been upheaved above the limit of the 

 snow-line. The consequent descent of glaciers having played an 

 important part in contributing their morainic debris to the formation 

 of these massive conglomerates now lying at the base of both the 

 1 Geographical Society's Journal for 1895. 



