part 1] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxxv 



tinuous and are responsible for practically all the features, there 

 •are still wider areas, uncoloured on the map, in which there is a 

 mingling of solid outcrops and patches of drift. This condition 

 prevails over the greater part of the North Midland counties and 

 much of the South Midlands ; and in such country it is often 

 difficult to decide in what degree the shape of the land has been 

 modified by the glaciation. Generally there is evidence of very 

 severe erosion since the drifts were deposited ; and most of the 

 present features appear to be due to this erosion. The patches of 

 drift occur sometimes amid areas of bare rock which might other- 

 wise have been supposed to lie beyond the limits of glaciation. 

 The question constantly arises whether these patches are the 

 remnants of a once-continuous sheet, perhaps representing an 

 older glaciation than that which left the thick cover in our east- 

 ern and north-western counties, or whether they were scanty and 

 discontinuous from the first. That their dimensions have been 

 considerably reduced is often evident ; but in their composition 

 and mode of occurrence they frequently carry indications of 

 original limitation and local incidence. Particularly is this the 

 case with the sporadic mounds and ridges of sand and gravel, that 

 occur in numerous places at relatively high elevations and are 

 shaped in a manner inexplicable except as indicative of local accu- 

 mulation. The isolated patches of boulder-clay, also, are found 

 mostly in hollows or sheltered places amid the ' solid ' outcrops, 

 where it is conceivable that the material may have been trapped, 

 while the main unimpeded ice-flow carried the rest of its burden 

 forward to its periphery. I should like to have discussed some 

 specific instances of this type which have come under my notice, 

 but find it impossible to do so within the scope of this address. I 

 must content myself, therefore, with the general statement of my 

 opinion that, in most places, where the drift is patchy now in the 

 Midlands, it was always patchy, and is not the remnants of a once- 

 continuous covering. It is, in fact, more remarkable that the ice 

 should anywhere have left such extensive sheets of drift as those 

 of the East of England, than that it should have passed over some 

 of the country without leaving much trace of its passage. In 

 almost all areas of present-da}^ glaciation it is a matter of common 

 occurrence to find bare rocky tracts, known to have been covered 

 by ice not long ago, on which there is nothing except an occasional 

 erratic to mark the event. 



In the Central Midlands there can have been little ' back- 



