1853.] TRIMMER ON THE GRAVELS OF KENT. 289 



taining irregular seams of gravel, and resembles much of the sand and 

 gravel associated with mammalian remains at lower levels, in the 

 ancient alluvium of the Thames. In other parts it is made up chiefly 

 of masses of unabraded flints. In this section the gravel rests on 

 chalk ; but at a little distance to the south, there is a patch of eocene 

 sand between them, as may be seen on the ascent from Dartford, on 

 the Rochester road. 



The surface of the chalk has been eroded into pipes of various 

 depths, generally from 3 to 5 feet, occasionally extending to the 

 whole depth of the chalk exposed, which is more than 30 feet, and 

 appearing not to terminate at that depth. These pipes are filled 

 with the gravel, not with eocene sand ; and the gravel having been 

 removed for ballast, over an area of about 80 yards by 1 2, these pipes 

 are shown to be connected with furrows, which through the space 

 exposed have a north and south direction. 



The gravel is covered by a deposit of loam, containing fractured 

 flints, and passing occasionally into gravel and chalk rubble, or re- 

 constructed chalk. Similar deposits have been recently described by 

 several eminent geologists, under the names of "head*," "angular 

 flint driftf," "Sangatte drift];," and "cretaceous and subcretaceous 

 drift §." 



Amidst this perplexing variety, I may perhaps be permitted, at 

 any rate for the present, to use the name of " Warp-drift," under 

 which I described it when I first drew attention to it as it exists in 

 Norfolk II ; and in fact wherever I have examined the superficial de- 

 posits in England, Wales, and Ireland, both where the erratic tertiaries 

 are present and where they are absent. This loamy warp-drift not 

 only covers the gravel, but fills a set of smaller pipes and furrows in 

 the chalk ridge on which the gravel rests, wherever that deposit has 

 been removed by denuding action. We have therefore, in this part 

 of Kent, three sets of these pipes and furrows ; viz. those filled with 

 eocene sand and green-coated flints ; those filled with the ferruginous 

 flint-gravel of Dartford ; and those filled with warp-drift and white 

 vmabraded and fractured flints^. The last are by far the most nume- 

 rous. Along the course of the railway, between this cutting and 

 Greenhithe, the surface of the chalk exposed in the cuttings is gene- 

 rally lower than at this spot, and is covered by warp-drift under all 

 its varying forms. It frequently exhibits alternation of deposit. At 

 the base there is often a collection of angular flints. Above this, a 

 foot or two of loam, resembling a deposit from tranquil water. This 

 occurs where there are hollows in the chalk ; over this again there is 

 a mixture of loam with white flints, or patches of ferruginous gravel, 

 or both ; the gravel resembling that of the neighbouring high 



* Quart. Jouin. Geol. Soc. vol. vii. p. 121. f ttid. p. 349. 



X Ibid. p. 274. § Phil. Mag. /. c. 



II Journ. R. Ag. Soc. vol. vii. p. 465, vol. xii. pp. 475, 489. Quart. Journ. Geol. 

 Soc. vol. vii. p. 24 ; Par. 15, pp. 29, 32, 35, 36, 202 ; also in a paper withdrawn 

 for separate publication and not yet published, vol. viii. p. 273. 



\ Proc. Geol. Soc. vol. iv. pp. 6, 482 ; Quart. Journ. Geol. Soc. vol. vii. p. 23 ; 

 vol. viii. pp. 244, 276 ; and unpublished paper, vol. vii. p. 273. 



