290 Rev. T. G. Bonney — On a Quartz Boulder in a Coal-seam. 



strong enough to have transported such a Boulder could have hardly- 

 failed to throw down grit enough to spoil the neighbouring coal. 

 At the same time it must have been brought by a swollen stream, 

 for otherwise whatever acted as a float could hardly have penetrated 

 the dense mass of vegetation constituting the coal-seam. The only 

 agents that appear likely to have transported it are ice or a tree. 

 The former does not appear a probable one at this period of the 

 world's history ; the Boulder, however, could readily have been 

 brought entangled in the roots of a tree, which might have been 

 torn up during some unusually high flood, have been swept by an 

 eddy out of the course of the main current, and have been left in 

 the jungle on the retreat of the water. In process of time the tree 

 would be imbedded in a coal-seam, and any trace of it would easily 

 be overlooked by the workmen. The finer sediment would be washed 

 out on the journey. 



(2). The locality whence this Boulder came is a hai'der question 

 to determine. There are quartzites at the Wrekin and the Stiper 

 stones, but not, I believe, exactly of this kind. The two localities 

 known to me where a similar rock occurs within a moderate distance 

 are Hartshill, near Nuneaton (to the S.E.), and the eastern side of 

 Bi'omsgrove Lickey (to the S.). The former of these is supposed to 

 be an altered Millstone-grit ; the latter is of Upper Llandovery age. 

 Both resemble the rock of the Boulder and of the Bunter con- 

 glomerate ; the former most closely. But not only is it in the 

 highest degree probable that both these quartzites were buried 

 beneath many fathoms of strata in the Triassic age,' but also, if we 

 regard the distribution of the Bunter pebbles, it is almost impossible 

 that they can have furnished the materials. Again, the South 

 Staffordshire Coalfield is on the northern slopes of the great barrier 

 which in the earlier Carboniferous periods separated the northern and 

 southern sea-basins, and this, if ever quite overspread by Coal- 

 measures, would not be till rather late in the period. Thus we are 

 driven to seek a northern rather than a southern origin for the 

 Boulder. The sedimentary materials, as Mr. Hull has shown in a 

 very able paper,^ during the Triassic as well as the Carboniferous 

 period came from the N. W., passing through the open space between 

 Cumberland and Wales, then probably the embouchure of a great 

 river. The Bunter pebbles, however, seem rather to have come from 

 the N.E., brought by the current of another stream (which may 

 have drained a considerable area to the eastward of the Firth of 

 Forth), or possibly rolled along the coast-line of the Pennine chain, 

 as in later days the pebbles washed out of the Boulder-clay have 

 travelled down the eastern shores of England. He suggests that 

 they have been originally derived from the quartzites of the 

 Northern Highlands, and have halted on the way in conglomerates 

 of intermediate age. With this opinion, after examining several 



^ If the Hartshill rock he Millstone-grit, it would probably be unaltered at this 

 rather early epoch of the Coal-measures. 



^ Quart. Joiirn. Geol. Soc. xviii. p. 127; and Triassic and Permian Rocks of the 

 Midland Couniies (Memoir of the Geol. Survey), p. 60. 



