8 



JOHN CORDEAUX: LINCOLNSHIRE. 



the boulder drift, a reddish clay filled with fragments of chalk and 

 derivative rocks, and varying from 50 to 300 feet in thickness. A 

 peculiarity of the low-lying districts near the sea, as at Tetney and 

 Great Cotes, are the ponds, locally known as ' blow-wells,' popularly 

 supposed to be unfathomable; they are powerful springs, never failing 

 in the driest season, rising from the chalk through the superincumbent 

 drift and alluvium. The blow-wells in the parish of Little Cotes 

 supply the town of Grimsby with an unfailing source of pure water. 

 Many of the low-country springs in the north-east districts are more or 

 less intermittent, the flow of water being regulated by the ebb and flow 

 of the tides. Mr. Clement Reid's recent researches in the north of the 

 county, more especially in connection with the old coast line at the 

 base of the wolds,* and the deposits of inter-glacial sands have added 

 much to the geological interest of the district. t The examination 

 of the sand pits at Laceby and Croxton has resulted in the 

 determination of numerous species of marine shells, some yet common 

 on the coast, others slightly northern, but not Arctic, whilst some are 

 indicative of a comparatively warm and equable climate. An 

 interesting find at Croxton is Corbicula flwninalis, of which living 

 examples are now restricted to the Nile, the lake of Gennesareth, and 

 some rivers of Asia. This shell is extremely abundant at Kelsey Hill 

 ballast pits, north of the Humber, in conjunction with bones of bison, 

 leptorhine rhinoceros, and elephant. A narrow band of red chalk 

 known as the Hunstanton red chalk is traceable all through Lincoln- 

 shire from Gunby to South Ferriby. The summit of the wold near 

 Pelham's Pillar is 456 feet above sea-level; the highest point is probably 

 near Normanby clump, about 549 feet. On the western slope of the 

 wolds below Caistor, and running south, there are a series of ironstones, 

 sandstones, and clays to which the term Neocomian has been applied. 



Still following the sectional line we find the Kimmeridge clay 

 represented in a narrow band, estimated at 600 feet in thickness ; 

 then in succession Oxford clay and Kellaway rocks, passing into the 

 cornbrash and great oolites, forming an elevated belt of varying 

 breadth through the length of the county. The Liassic clays and 

 marlstones are defined by a narrow belt ten to twelve miles wide in 

 the south, and running off" to a mile in width near the Humber. 

 Lastly, on the slopes of the Trent Valley are the oldest rocks in the 

 county, the Keuper sandstone. 



* At this period the coast line of Lincolnshire was represented by a chain of low- 

 lying islands of chalk, separated by narrow and deep fiords. 



f'The Geology of Holderness, and the adjoining parts of Yorkshire and 

 Lincolnshire.' Memoirs of the Geological Survey, 1885. Clement Reid. 



Naturalist, 



