Reports and Proceedings — Geological Society of London. 239 



2. " On the Kelations of the Chalk and Boulder -clay near 

 Eoyston (Hertfordshire)." By Professor T. G. Bonney, Sc.D., 

 LL.D., F.K.S., F.G.S. 



On the uplands south of Eoyston, Mr. H. B. Woodward, F.E.S., 

 has described three sections,^ which in his opinion indicate that 

 a great ice-sheet, as it advanced from the north, sheared off large 

 masses of Chalk and mixed them up with its ground- or englacial 

 moraine (the Chalky Boulder-clay). 



The author points out that this interpretation rests on an 

 hypothesis — namely, that the latter deposit is the direct product of 

 land-ice — which, as it involves some serious difficulties, cannot yet 

 be taken for granted. For instance, this clay in many parts of 

 England contains chalk pebbles, more or less well-rounded, and 

 often striated. But it is improbable that fragments of rock in 

 either a ground- or an englacial moraine would be shaped into 

 ordinary pebbles ; and they would be brought into contact so 

 seldom, and for so brief a time, that they would be but little 

 scratched. But these chalk pebbles resemble those formed by 

 water, either in a river-bed or (more probably) on a sea-beach. 

 How, in the latter case, they could be striated Colonel H. W. Feilden 

 showed twenty-eight years ago. 



That ice is capable of shearing off and thrusting before it large 

 masses of rock, is also an hypothesis, for which the author, after 

 doing his best to study ice-work in the field, can find no valid 

 evidence. He maintains that these sections do not suggest the 

 above explanation. Passing over that "north of Eeed " as un- 

 important, we come to the Pinner's Cross Pit. Here the Boulder- 

 clay is not, strictly speaking, ' banked up ' against the Chalk, 

 as stated by Mr. Woodward, but occupies a hollow in the Chalk, as 

 described by the late Mr. Penning. The Chalk has a fairly high 

 dip, but there is little other sign of mechanical disturbance. In the 

 pit south-west of Newsell's Park, a shear-plane can indeed be seen 

 in one face, which, however, is explicable by ordinary faulting ; and 

 on the same face there are (or were) some small clayey patches. 

 A few yards farther to the south-east. Boulder-clay appears above 

 the floor of the pit, filling an arched cavity. This is, no doubt, 

 a singular position, but there is nothing to show that the Chalk has 

 been thrust over the Clay. The author suggests that, as in Moen 

 and occasionally in Eiigen, the Clay has been carried down from 

 above into cavities already formed in the Chalk, and quotes a case 

 from the latter island of a clay-filled cavity, which was connected 

 with the surface and might have yielded a section like that in the 

 above-named pit. Penning's diagram shows (probably nearly over 

 this spot) Boulder-clay resting upon the Chalk. So the author 

 maintains that, even if the fundamental hypotheses be true, they 

 are not applicable to these sections. 



3, " Brachiopod Homoeomorphy : Pygope, Antinomia, Pygites." 

 By S. S. Buckman, F.G.S. 



1 Quart. Journ. Geol. Soc, vol. lix (1903), p. 362. 



