i6 



fairly accurately with those found in rock successions of the same 

 range in Wales and England. 



As before, he contented himself with publishing the facts he 

 had collected, denying himself even the satisfaction of correlation 

 with Moffat, leaving it to be inferred by those sufficiently interested 

 to compare the two papers, from the facts brought forward, (i) 

 that the succession of graptolites was the same ; (2) that, though 

 the rock-succession was about ten times thicker than at Moffat, 

 the rock-grouping corresponded in the two areas ; (3) that many 

 zones in one area were continued into the other ; (4) that for 

 correlation with other regions the graptolites of Moffat and Girvan 

 had proved successful where the trilobites and brachiopods of Girvan 

 had previously broken down. 



*" The discovery of these graptolite zones in the Girvan area 

 threw a flood of light on the stratigraphical horizons of that com- 

 plicated region. He was thus enabled to demonstrate that 

 Murchison had been misled by the apparent synclinal arrangement 

 of the strata on the plateau on the south side of the Girvan valley, 

 and that he had thus erred in placing the Pentamerus grits of Saugh 

 Hill on a lower horizon than the graptolitic flagstones of Ardwell 

 and Penwhapple Glen ( Ardmillan series) . Over much of that region 

 the beds are inverted and hence no reliable conclusions can be based 

 on mere superposition." 



As this paper was called Part I, it is to be presumed that 

 Lapworth intended to follow it up with a sequel devoted to the 

 palaeontology founded on his own and Mrs. Gray's collections, 

 and probably also to the tectonics of the area, and the correlation 

 of the rocks with those at home and abroad. The nearest approach 

 to the former was his list of Scottish fossils prepared in 1876 for 

 the meeting of the British Association at Glasgow. For the latter 

 we have his paper on ' the Ballantrae Rocks of South Scotland, 'f 

 published in 1889 (44). 



5. The Ballantrae Rocks (44). 



In this memoir Lapworth not only described his work on the 

 Ballantrae igneous rocks associated with which he had found 

 graptolite-bearing strata of Arenig and early Llandeilo ages but 

 he gave detailed comparisons of the sequences in various parts of 

 South Scotland. To this he added tabular correlations with the Lake 

 District, Wales, and the West of England, drawing parallels with 

 the zones so far established in each area, and giving a generalised 

 account of the variations in lithology and thickness as the rocks 

 are traced from one locality to another. 



* The Silurian Rocks of Britain, vol. I, Scotland (1899), p. 30. 

 t 44- 



