270 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 23, 



the London clay to the chalk. It may, with fig. 14, serve to show 

 the general relative position of stratum " c " to the chalk, but ex- 

 hibits neither the thickness nor the variety usual in this lower series. 

 (See fig. 15.) 



Fig. 15. — Section near Hatfield. 

 E. w. 



2- «■ Gravel— roughly-rounded flint, white quartz, and other 

 ^^ pebbles, in nearly white sand. 



b . London clay ; a very dark grey and brown clay passing down- 

 wards into a yellow sandy clay. 



c. Sandv bro^Tn clav, mixed in its lower part with a few 

 round flint pebbles. Organic remains not numerous. 



(The division between "6" and "c" is not weU marked, 

 and should probably be placed lower.) 



1 . A series of thick beds of light yellow and ash-coloured 

 sands, mixed in places ^vith clay. 2. Coarse green sand 

 and clay, full of large, partly rolled, green-coated flmts. 



. /.Chalk. 



The only fossils I could here determine were an Astarte much re- 

 semblmg the species common at Heme Bay, Ostrea, and teeth of 

 LamncB. Fragments and traces of other shells requiring further ex- 

 ammation are met with. ' Thence by Essenden* to Hertford no sec- 

 tions of this bed are exposed. The next one is m a brick-held on 

 George's Farm, one mile south-east from Hertford on the London 

 road. (See fig. 16.) 



Fig. 16. — Section near Hertford, 



Brovm. clav mixed with flint gravel. 



rLondon clav; grev and vellow clay passmg downwards 



into dark 'grev sandy clav. Casts of shells m clay and 



\ pieces of soft brown wood not uncommon . The lower 



1 partof this probably belongs to "c." 



Il^und flint pebbles in brown clay, -nith a few teeth ot 



LamncB. 4 to 8 inches. •,■,.! 



Light sree-ish sand, with traces of mottled red clay, 

 passing down into light ash-coloured sand. 



The chalk outcrops at a depth of about thiily to forty feet below 

 "c " The organic remahis here found in the lower part ot ' 6 and 

 in - c " are not numerous, and are badly preserved in the form of soft 

 clay casts. Sufiicient, however, of them^ remams to determme with 

 but httle doubt the undermentioned species :— 



* In a well dug here, I am informed that a mass of shells teu feet thick occurred 

 immediately below the London clay, at a depth of 100 feet. 



