236 Correspondence— G. W. Lamphigh. 



remained without essential change, and that my critirs and I are 

 discussing the same facts in this particular. 



Dr. Kitchin and Mr. Pringle rely for proof of the inversion almost 

 entirely upon inferences drawn directly or indirectly from the 

 fossils of the limestones and its associated strata. They infer that 

 the fossils in question — certain brachiopods, lamellibranchs, 

 Crustacea, and echinoderms — cannot occur in place below the Gault. 

 But if the stratigraphical evidence is convincing, as I believe it 

 is, that at this locality they do occur below the Gault, the a priori 

 inference loses all validity. I presume that no geologist will claim 

 that our present knowledge of the range of these particvilar fossils 

 is so ])erfect that it cannot be extended. In strata so sparingly 

 and sporadically fossiliferous as the upper part of the Lower Green- 

 sand, w^e know as yet very little about the life of the period. Now, 

 the Shenley section, as I believe, has slightly extended our know- 

 ledge ; and, in the paper of 1903, my co-author and myself offered 

 what I still hold to be a reasonable explanation of the unusual 

 elements of the fauna. Our critics naturally lay stress upon their 

 own side of the argument, and dismiss the admixture of Lower 

 Cretaceous forms as ' derivatives ' and as occurring, perhaps, in 

 a limestone similar to the so-called ' Cenomanian ' rock, but of 

 different age, and brought into contact with it by the inversion. 

 I hardly need express dissent from these inferences ; they merge 

 into the broader question of the supposed Glacial overturn. Let us 

 consider what this hyjDothesis implies, and liow far it runs contrary 

 to probability. 



L The supposed ' Cenomanian ' limestone, a gritty rock of 

 ]jeculiar aspect and composition (fully described in our paper of 

 1903), is unlike any other rock known in the district, and shows every 

 indication of having been formed on the floor on which it now rests. 

 My critics have sought for it above the Gault all along the foot of 

 the Chalk escarpment, and acknowledge that they have sought in 

 vain. They fall back upon an assumption that it may have occurred 

 above the Gault in a vanished tract in the neighbourhood of Shenley 

 Hill, and that it may have remained at the surface there until the 

 hypothetical inversion in Glacial times. Yet it is only a few inches 

 thick, and is for the most part quite fresh and un weathered. 



2. In the same way the bed of loose glauconitic greensand, up to 

 5 feet thick, which I saw below the Gault, surrounding an upstanding 

 crag of iron-grit, in the easterly part of Garside's pit before the 

 working was abandoned in 1906 (see Proc. Geol. Assoc, vol. xx, 

 p. 475), is supposed to have been overturned from the surface ; 

 yet it also, though so readily perishable, shows no trace of weathering. 



3. The slab of Gault, greensand, and limestone supposed to have 

 been overturned has proved to extend without visible disturbance 

 over an area of not less than 15 acres, and it still has a thickness of 

 about 18 feet in Harris's pit, which, therefore, must be accepted 

 as the minimum for the whole slab before the overturn. Not a trace 



