86 SECTIONAL ADDRESSES 



I consider that the facts in this eastern region support the idea of two 

 distinct glaciations within the Older Drifts with interglacial conditions 

 between them {First biter glacial). The question of how the lower, 

 very ancient chalky boulder clays of Coventry and Rugby reached that 

 district remains to be solved. 



West of the Derby-Moreton line the area of the Older Drifts is sharply 

 limited on the north by the southern edge of the later Main Irish Sea 

 glacials (Fig. 4), which has already been discussed. Except in the Lower 

 Avon valley, the older drifts are here Welsh. The directions of ice-flow 

 are shown on Fig. 3. 



The interpretation of these drifts is extremely difficult, partly because 

 it is likely that if there have been two glaciations, they will be recorded 

 by similar deposits which might occur each separately or both together 

 on the same surface, and partly because of the great dissection and de- 

 struction that they have undergone. Many of the deposits, too, are gravels 

 and sands that belonged rather to outwash fans than to the ice sheet 

 itself. On the other hand, we have, as already pointed out, the river 

 terraces to help us, by providing a record of the progressive deepening of 

 the valleys and of the contemporaneous opening up and development of 

 new lines of drainage on surfaces, each of which appear to grade with one 

 or other of the terraces, and which for this reason may be regarded as of 

 approximately the same age as the terrace in question. 



One is bound to confess that any conclusions that can at present be 

 drawn are very tentative. For this reason I hesitated about setting them 

 out in black and white as diagram maps ; but I have decided to do so in 

 order to make clear my present views. It is most essential, however, 

 that the speculative nature of the maps (Figs. 3 and 5) be continually 

 kept in mind. They attempt to express, diagrammatically, the general 

 distribution of the ice and of the main drainage lines at successive stages 

 in the melting of the glaciers, which I think can be deduced from the dis- 

 tribution of the drifts, from their composition, and from their relation 

 to the terrace history of the Severn and Avon. 



We may consider the Lower Avon and Lower Severn vales first. Here 

 the highest deposit, namely the Woolridge Terrace, is developed between 

 Tewkesbury and Gloucester, and up the Leadon valley at heights between 

 200 and 285 O.D. I have elsewhere suggested that the Leadon valley 

 deposits were laid down by water travelling west of the Malvern range 

 and forced to take this course by the filling of the Severn vale by the 

 Welsh ice, when at its maximum (Fig. 3, i). At this stage, too, the ice 

 seems to have carried Welsh boulders to the Moreton-in-the-Marsh 

 district and to have been responsible for certain very high level drifts 

 in Worcestershire. For these reasons I picture it as stretching over the 

 vales of Severn and Avon to the Cotteswold escarpment. A slight retreat 

 (Fig. 3, 2) would have allowed outwash material to be laid down below 

 Tewkesbury. Patches of this have survived at Woolridge (260 O.D.), 

 Norton Hill (283 O.D.), and Corse Hill (250 O.D.). These and some 

 other very high deposits such as those already referred to (p. 82) at 

 Dripshill (240 O.D.), and Leopards Grange (320 O.D.), and at Cracombe 



