PRESTWICH — WOOLWICH AND READING SERIES. 93 



Sands, there is in these sections no evidence to show. I am inchned, 

 however, to think that a portion, if not the whole of them, may pos- 

 sibly belong to the former group*. According to the Rev. W. B. 

 Clarke, the evidence of its extension in Suffolk is more definite f. In 

 well-sections at Harwich (p. 370) he mentions the occurrence of beds 

 of mottled day, sand, and shingle ; also of vegetable impressions in 

 a brown clay at Higham Bridge (p. 373) J. 



It would thus appear that mottled clays, irregularly interstratified 

 with sands, prevail along the western portion of the northern outcrop 

 of the Woolwich and Beading series, whilst north-eastward this series 

 seems reduced generally to a simple thick bed (or beds) of sand. 

 With the exception of the Ostrea Bellovacina found occasionally at 

 the base of this group, no other shells are met with along that line. 

 There is nowhere any appearance of the Woolwich group of fluviatile 

 shells, but traces of vegetable matter and teeth of Lamna occasionally 

 occur. 



As the surface-sections do not afford us sufficient proof of the exact 

 connection of the sands and mottled clays of Beading with the sands, 

 clays, and pebble beds of Woolwich, we must retrace our steps to 

 Uxbridge and Watford, and endeavour to follow the continuation of 

 these beds underground to London and Woolwich. Although passing 

 through a district in which several deep wells have been sunk, there 

 are, owing to the want of correct details, but a few amongst the 

 number which are available in evidence. 



First is the well at the Hanwell Lunatic Asylum, of which general 

 particulars were taken § and rock-specimens || preserved. 



* The foreman at the Kyson pit stated that large oysters {Ostrea Bellovacina ?) 

 were occasionally found in the sand beneath the pebble bed with the mammalian 

 teeth. 



t Trans. Geol. Soc. 2nd ser. vol. v. pp. 361-383. 



X In many of this author's sections, some beds, which are described as " Lon- 

 don Clay," " Plastic Clay," and " Plastic Sand," will, I believe, be found to belong 

 to the Boulder Clay and the unproductive sands of the Crag (Nos.33, 40 and 43, 

 p. 376; Nos. 44 to 49, p. 377 ; Nos. 55, 56, 59, p. 378 ; No. 65, p. 379). At 

 Balingdon Hill (p. 375) there should be 30 to 40 feet of the unproductive sands 

 of the Crag and of the Lower Tertiary Sands between the diluvial clay and the 

 chalk. These errors of description detract from the weight to be attached to this, 

 in other respects, valuable document. 



Since writing the above, I have learnt that in an artesian well at Colchester 

 the " Lower London Tertiaries " were only 30 feet thick (Brown, Ann. & Mag. 

 Nat. Hist, for October 1853). 



§ In the well-sections the names given by the well-digger are throughout re- 

 tained. I have however, in most cases, added another column with the geological 

 grouping, as I interpret the descriptions, in italics. The italics in parentheses are 

 also introduced in explanation of some of the terras. 



It will be observed that the " Basement Bed of the London Clay " rarely 

 api)ears in these sections. This I beheve arises from the fact that, owing to its 

 general thinness and not very striking mineral characters, it has been almost always 

 overlooked in well-sections. Wherever specimens have been preserved, I have 

 generally found evidence of its existence. 



I may remark that many of these deep wells have been sunk within the last ten, 

 and all within the last thirty or forty years. 



t Amongst the specimens which I have examined, there were the following 

 London Clay shells, but they were loose and not placed : — Cancellaria Iceviitscula, 

 Cytherea ohliqua, Fusus bifasciatus, Natica, Nucula Bowerbankii, Panopcea inter- 

 media, Rostellaria Sowerbyi. 



