360 The Rev. Prof. Blake— Base of the Sedimentary Series. 



with the ArchEeans were brought to-day, though with the aid of 

 a fault. 



With regard to the relations of the Longmynd series to the A T olcanic 

 masses on the eastern side, they were stated to be separated by a 

 fault, so that no conclusion could be drawn from observations here. 

 About three years ago Dr. Callaway began to think that the Longmynd 

 series itself, which had always been assumed to be Cambrian, but 

 which, as a matter of fact, according to his observations, was every- 

 where separated by faults, might not, perhaps, belong to that system. 

 The relation of the Longmynd rocks on the west of the volcanic 

 group to the quartzite on the east not having been demonstrated, 

 their correlation was always difficult; but even if the Longmynd 

 were Cambrian, it seemed most probable that they represented an 

 earlier part of it than the quartzite. The lower down, therefore, 

 the quartzite is, the less room is there in the same system for the 

 Longmynd rocks. Eecently, according to the statements of Prof. 

 Lapworth, the quartzite, or rather its associate, the Comley sand- 

 stone, has been shown to contain the oldest known Cambrian fauna, 

 and therefore to be very near, if not at, the base. This would leave 

 no room in the Cambrian for the Longmynd series, and " render 

 their Precambrian age a matter of fair probability." 



According, therefore, to these observations and views, there may 

 be three or even four distinct Precambrian formations in Shropshire. 

 The highest would be the "Longmyndian," isolated from all others, 

 but containing pebbles of the next series. Then the volcanic group 

 or " TJriconian," isolated from the Longmyndian, and giving no clear 

 stratigraphical indications of its relations to the next, but containing 

 pebbles of it in its conglomerates ; and then the " Malvernian," 

 regarded as the oldest and most metamorphosed of all. In some 

 undefined position with relation to these is a mass of schists (which 

 has not yet been called the " Rushtonian " !) 



I have now to state the bearing of my recent researches in the 

 district on these conclusions. From what I had seen previously of 

 the Longmynd and Wrekin, and what I had learned elsewhere, I 

 had accepted the conclusion that the '• Uriconian " rocks were older 

 than the '■ Longmyndian," and having suggested that the latter were 

 Upper Monian, the former became Middle Monian, and, as I then 

 thought, in part equivalent to Pebidian ; and I thought to find evidence 

 of the correctness of this view, which differed only, if at all, from 

 that of Dr. Callaway, in assigning a definite age to the Longmynd 

 group. But facts are stronger than views. In studying the Long- 

 mynd series I found there was on the whole great regularity, in the 

 lower part ; but that, on reaching the conglomerates and grits, great 

 irregularity was displayed. While the eastern members of the series 

 marched straight across hill and dale, scoring the slopes with the 

 edges of vertical beds, the western portion commenced with 

 horizontal boundaiy -lines, and displays of outliers and inliers ; in a 

 word, there was an unconformity between the grits and conglomerates 

 on the west and the underlying slates and greywackes on the east, 

 the latter coming in contact with different subdivisions of the former, 



