264 



GEOLOGICAL NOTES. 



About lOo yards south of Hatch Lane there were some 

 curious pipe-like hollows in the surface loam on the western side 

 of the cutting, the origin of which seems at first sight not easy to 

 explain. It appears to me that in this matter we shall obtain 

 light from the appearances presented where the artificial bank 

 bounding the channel of the present Thames has excluded a 

 certain portion of the alluvial flat. In the excluded portion we 

 see river deposits exposed to influences to which they were 

 everywhere subject before man embanked the stream. In the 

 surface loam are many irregular hollows, begun as broad surface 

 cracks and deepened by rain. Similar hollows in old deposits 

 would become liable in times of flood to be more or less filled 

 with water bringing with it fine gravel and sand. Probably the 

 hollows shown in Fig. 2 also owe something to the influence of 



.9 N 



Fig. 2. Pipe-like hollows in the loam S. of Hatch Lane. 



1 - loam. g =: gravel. 



Height of section about, lift. Breadth 22ft. 



ice. The kind and amount, however, of the ice-action they 

 suggest is not that of the Glacial era during the deposition of 

 the Essex Boulder clay, but rather that of a severe winter of the 

 present day, such as occurred in 1894-5. Then we saw the 

 Thames covered with blocks of ice which floated up with the 

 tide and became stranded here and there during the ebb. 

 Masses of this kind floating in the more ancient Thames would 

 not as now, be confined to its channel, but would often be 

 deposited, during exceptionally high tides, over the adjacent 

 alluvial flats. In some cases they would bear with them a 

 certain amount of sand, gravel or animal remains. And they 

 would be extremely likely, through the very variable amount of 

 pressure on the surface loam, caused by their irregularities 



