THE 



GEOLOGICAL MAGAZINE. 



No. LXIII.— SEPTEMBER, 1869. 



I. — The Freshwater Deposits of the Valley of the Lea near 

 Walthamstow, Essex. 



By the Editor. 



OWING- to the great increase of the population of the Eastern parts 

 of London, the East London Water Works Company have been 

 engaged for several years past, in constructing most extensive 

 Eeservoirs for the storing and filtering of Water. 



These Eeservoirs commence near the Lea-Bridge road, and extend 

 thence in a northerly direction beyond the Tottenham Railway 

 Station, and occupy a large tract of the Lea Valley, known as the 

 Walthamstow Marshes. 



About a quarter of a mile from the Great Eastern Eailway at 

 Tottenham, between the Mills and Higham Hill, two large Eeser- 

 voirs are now in process of excavation, covering together more than 

 one hundred acres. 



The depth penetrated over the whole area of the floor of the 

 Eeservoirs probably nowhere exceeds, on an average, 10 feet, but 

 the trenches made for the "puddle-walls" in the centre of the 

 artificial embankments which enclose the Eeservoirs, go down to a 

 depth of 20-24 feet. 



The materials removed are all of Post-Tertiary age, and consist of 

 surface-soil, loamy clay, j)eat, shell-marl, coarse and fine sands, 

 rounded and sub-angular gravels from the Chalk and Woolwich 

 series, with pebbles of chert and sandstone from the older rocks. 



The beds above the gravel which forms the floor of the Eeservoirs, 

 vary in thickness and extent over the whole area. Thus, the shell- 

 marl or deposit consisting of a vast accumulation of Land and 

 Freshwater shells (the species of which are hereafter noticed), 

 varies in thickness from two inches to three feet, and occupies basins 

 or depressions in the vmderlying clay or gravel beds. 



Amongst the varied sections presented during the progress of the 

 works, the following will illustrate the order of succession of the 

 deposits cut through. 



VOL. VI. — NO. LXIII. , 25 



