J. W. JUDD ON THE SECONDAKY ROCKS OE SCOTLAND. 741 



group of the Shiant Isles probably represents the only remaining vestige of 

 another great volcanic centre, which has been almost wholly removed by the 

 denuding forces. 



The same map is made to illustrate the distribution of those isolated patches 

 of Secondary strata with which the present part of the memoir more par- 

 ticularly deals. As these exposures are not only of minute size, often, indeed, 

 even when comprising series of beds hundreds or thousands of feet in thickness, 

 covering no superficial area, but being displayed in absolutely vertical pre- 

 cipices under the almost everywhere superincumbent Tertiary volcanic rocks, 

 the ordinary mode of representing strata of different ages on geological maps 

 wholly fails us here. I have therefore coloured all the beds intervening 

 between the Paleozoic and the Tertiary of one uniform conspicuous tint, and 

 endeavoured by means of the lettering to show the ages of the various strata 

 seen at different points. In order that they might be visible at all on a map~of 

 this small scale, however, the areas covered by the Secondary strata have had to 

 be exaggerated in most cases. 



Fig. 2 illustrates in a somewhat diagrammatic way the relations of the 

 Secondary rocks to those older and younger than them respectively, especially 

 the preservation of outlying patches of the Secondary strata, and the effects 

 produced by the great post- Miocene fault of the Innimore of Ardtornish. 



Discussion. 



Prof. Ramsay remarked that the material placed before the 

 Meeting was so vast in amount and so condensed in form, that it 

 was impossible to grapple with all the author's statements. In 

 general he had nothing to object to what the author had said; and 

 probably if all the data had been laid before the Meeting, every one 

 would agree to the statements contained in the paper. But, no 

 doubt for want of time, the author had, it seemed to him, left some 

 matters a little obscure. Did he mean to imply that the whole area 

 of Scotland had once been overlain by Carboniferous strata? Prof. 

 Ramsay quite agreed that a large portion of the British Islands was 

 once so covered — three fourths of Ireland and a great part of 

 England — but, he thought, not all Wales, nor all the Highlands of 

 Scotland. His reasons were drawn from the history of the Palae- 

 ozoic rocks. In the case of the Old Red Sandstone of Scotland, Mr. 

 Godwin- Austen had proved this to have been deposited in fresh- 

 water lakes. The masses of Old Red conglomerate in Scotland were 

 sometimes of glacial origin, and were composed of the detritus of 

 older Highland Silurian rocks. There must then have been lofty 

 mountains for the origination of such glaciers ; and there was high 

 land during the Old-Red-Sandstone period. After the Old Red 

 Sandstone we find great flat territories, thin beds of limestone, and 

 of coal with underclays which partly showed estuarine conditions, 

 and there must have been dry land in the neighbourhood. Evidence 

 is still wanting to prove that the whole of the Highlands were 

 covered by coal-beds. With regard to the faults described by the 

 author, Prof. Ramsay thought such enormous downthrows as some 

 of those mentioned to be improbable. He would remind his hearers 

 that a fault may have great magnitude in one part, and die out to 

 nothing within a distance of a few miles. All the mountains of 

 Scotland were certainly not covered by Oolitic and Liassic strata. 



