Vol. 50.] BORINGS AT CULFOED, WINKFIELD, WAKE, AND CHESHUNT. 495 



and glauconite varies greatly, one slide having no visible quartz and 

 another very little quartz and no grains of glauconite, while iu the 

 third both are in fair quantity. 



Prom these observations and comparisons we think ourselves 

 justified in concluding that the Culford and Richmond limestones 

 are of the same age, and that they belong to the same group of rocks 

 as the Kentish Rag and the Pargate Stone ; that is to say, to what 

 is usually termed Lower Greensand, the beds which one of us pro- 

 poses to call Vectian, but for which Prof. Judd prefers the name 

 Neocomian. 



The fragment of an ammonite was submitted to Messrs. Sharmau 

 and Newton, who report that it is unlike any known Cretaceous 

 species, and most resembles Ammonites Valdani of the Lower Lias ; 

 at the same time, they say that the fragment is too small to be 

 identified with certainty, and that it might belong to some other 

 Jurassic species. It would appear, therefore, to be a derived fragment, 

 like those so frequently met with in the Lower Greensand, and, as 

 such, is useless for determining the age of the beds in which it was 

 found. 



So far as we can ascertain, no pebble-bed occurs at the base of 

 the Cretaceous series at Cull'ord : the account given being that the 

 boring-tool passed directly from the lowest calcareous stone into the 

 greenish claystone or slate. 



With respect to the Palaeozoic rocks, of which nearly 20 feet were 

 pierced in the boring, we are unfortunately able to say very little. 

 Those who have seen them differ greatly in opinion as to their age. 

 Mr. W. H. Dalton sees resemblances to the Wenlock Shales, and 

 would refer them to the Silurian system. He informs us that he 

 judged chiefly from a sample of soft shale containing "a bit of 

 limestone resembling that of Upper Silurian." As stated on p. 492, 

 we found this to be not a calcareous, but a siliceous rock. Dr. J. E. 

 Taylor writes that the softer shaly slate is like the shales found at 

 Harwich, and considers both to be of Lower Carboniferous age. For 

 ourselves we think there is nothing distinctive about them, and that 

 such shales and slates might occur in any cleaved area of Carboni- 

 ferous, Devonian, Ordovician, or Cambrian rocks ; but we do not 

 think they resemble the Upper Silurian rocks of Shropshire, and 

 that is the type of Silurian which occurs below Ware. There is 

 only one point on which all are agreed, namely, that these Culford 

 slates are older than the Coal-Measures. The angle and direction 

 of dip could not be ascertained. 



So far, therefore, as the samples preserved enable us to form an 

 opinion, the age and thickness of the several formations passed 

 through are as follows : — 



Pit (? in Drift) 



Upper and Middle Chalk .. 



Lower Chalk 



Upper Gault 



Lower Gault 



Vectian (Lower Greensand) 

 Palaeozoic rocks 



Thickness. 

 Feet. 



6 

 383 

 143 

 30 

 43 

 32* 

 19# 



Depth. 

 Feet. 



6 

 389 

 532 

 562 

 ti05 

 637£ 

 657J 



2l2 



