182 



PKOCEEDINGS OF THE GEOLOGICAL SOCIETT. 



10 feet of it. Unless there be any great rise of the chalk-floor east- 

 wards, towards Kilnsea and Dimlington, these borings would show 

 that the chalk at the latter places was upwards of 100 feet below the 

 beach. In that case the thickness of the basement clay exposed at 

 Dimlington (beneath nearly 100 feet of the purple clay) would, added 

 to this depth, give a total thickness of about 120 feet for the thickness 

 of the basement clay iri that part*. A similar uniformity in the 

 depth of the chalk-floor seems to be maintained along a line running 

 due east from Hull to Withernsea, as shown by three borings into 

 the chalk near Hedon, and by the borings along the Withernsea 

 Railway, given by Mr. Prestwich f, which, although not reaching the 

 chalk, showed 82 feet of deposits at Withernsea, a spot but Mttle 



Fig. 14. — Section constructed from the hoHngs for the Hull Docks. 



100 

 110 



Chalk, h. Sahd with chalk-rubble (bed h of coast-section, fig. 1). c. The Purple clay, 

 called in the borings "Brown stony clay with, sand threads." d. The Hessle sand. 

 e. The Hessle clay. /. Peat-bed with the stools of trees rooted into it and into e, 

 and with the stems lying flat in the peat. g. Silt abounding with TelUna solidula, 

 Scrohicularia pijperata, Cardium edule, &c. h. Salt water. The length of the sec- 

 tion is about one mile, the vertical scale being about eleven times the horizontal. 

 The numbers along the top denote the borings as numbered in the Dock Engineers' 

 record, being such of the borings as (with the exception of 1 and 5) run in a con- 

 tinuous line, about 80 yards from the shore. Nos. 1 and 5 being out of that line 

 and nearer the shore, the depth of the water Qi) is in their case disregarded. The 

 vertical numbers denote the depth below the datum line, which is that of high 

 water. The broken lines indicate the presumed continuation of the beds where the 

 borings do not descend to them. The portion of the section above the horizontal 

 line between the 30 and 40 feet mark is that which was fully exposed during the 

 subsequent excavations; but the excavations were in some parts carried deeper, 

 and into the purple clay (c). 



above the beach. Several borings at Hornsea gave, after deducting 

 the elevations of the places, the chalk at a depth of from 60 to 70 feet 

 below the sea-level. This, when the thickness of the basement 

 clay exposed in the cliff's north and south of this place is added, 

 would show that clay reduced at least one-third in thickness to that 

 possessed by it (on the assumption before made) at Dimlington. A 

 boring at the New Inn, Hornsea, gave the chaJk at a depth of 161 



* As showm in fig. 11, however, there is probably some upheaval in this 

 part which would involve a less depth for the chalk- floor, and consequently a 

 less thickness for the basement clay. 



t Quart. Journ. Geol. Soc. vol. xvii. p. 455. 



