10 



Shales, nine-tenths of which, including all the branching forms, 

 have disappeared in the Gala group. Twelve species have been 

 found in the Riccarton beds overlying the Gala Series. The Moffat 

 Shales are compared with the Utica and Hudson River beds of 

 America, and with the graptolitic shales of Wicklow and Wexford, 

 and are thought to be of Bala or Bala-Llandeilo age. The Gala 

 group has a fauna approaching that of the Coniston mudstones, 

 and also Barrande's ' colonies ' and stage E.e.i. of Bohemia. They 

 seem to be high up in the Lower Silurian, and probably the higher 

 beds are of Upper Silurian age. The authors demonstrate the 

 existence of a syncline of Gala rocks with the Moffat Shale north 

 and south of it, and that on each side the shale band is several 

 times repeated by folding or faulting. 



In a short paper (5) published in 1872, Lapworth categorically 

 states that he has convinced himself that all the black shale bands 

 are a single bed 500 to 600 feet thick, recurring again and again in 

 anticlines between which the conformable Gala greywackes occur 

 in repeated synclines. The black shales are divided into three 

 stages a Lower, parallel with the Llandeilo or Hudson River 

 beds ; a middle, like the Upper Llandeilo of Builth ; and an Upper, 

 supposed to be a Caradoc. Some of the groups are further divisible 

 into zones which can be traced from point to point. 



From this paper it is clear that Lapworth was now hard at 

 work on the Moffat region itself. By this time also his studies had 

 convinced him that the application of the simple rules and 

 methods appropriate to little-disturbed rocks, to a region in 

 which complicated structure might be concealed, would be highly 

 dangerous and likely to lead to an utterly erroneous interpretation 

 of the geology. He therefore set to work to map its 300 square 

 miles in minute detail with the use of topographical maps on the 

 largest scale he could obtain ; and, where these were not large 

 enough to record and depict the structures observed, surveying 

 the ground and constructing his own maps on a sufficient scale. 



At the same time he applied himself to the study of all the 

 literature, English and foreign, on the graptolites, which he realised 

 were the only organisms likely to afford him any assistance in 

 identifying horizons in the monotonous black shale bands. He 

 also visited other graptolite-localities, such as the Coniston and 

 Stockdale areas, and studied graptolites collected by other geologists, 

 such as those from Co. Down and St. Davids. 



Further stages in his work are revealed in 1876, when he 

 grouped together the Birkhill and Gala as one Formation, which 

 he named Valentian (*) and compared with the Lower Llandovery, 

 May Hill, and Tarannon Series. At this time he also effected 

 tabular correlations of this and lower divisions. 



* 13, pp. 1,2. 



