284 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Feb. 5, 



Maximum Thicknesses of Beds within the Area described. 



feet. 



Oxford Clay uncertain. 



Cornbrash , 15 



Great Oolite— Clay 20 feet. 



„ Limestone 25 „ 



„ Upper Estuarine 33 „ 



78 



Inferior Oolite — Lincolnshire Limestone .... 75 feet. 



„ Northampton Sand — 



Lower Estuarine 18 feet. 

 Ferruginous beds 60 „ 



78 „ 



153 



246 



A few words as to the extent of the area occupied by the Lincoln- 

 shire Limestone. It ranges through the whole of the county of 

 Lincoln, stretching into South Yorkshire on the north, and through 

 Rutland into Northamptonshire on the south. The length of this 

 outcrop (three fourths of which is in Lincolnshire) is about 110 

 miles. In Northamptonshire, its greatest apparent width across the 

 strike is about 16 miles. It attains to its greatest thickness in 

 Lincolnshire, exceeding near Sleaford 200 feet. Mr. Judd (who 

 has " beaten its bounds ") considers that it had originally an 

 elongated lenticular form, and probably thinned away irregularly 

 in every direction from the point of its greatest thickness. In Lin- 

 colnshire, its eastern boundary is hidden under superincumbent beds 

 of other formations; and its western boundary, to a very great 

 extent, has been pared away by the denudation which scooped out 

 the great valley of the Witham and the Trent. 



It is probable that the Lincolnshire Limestone and the Northamp- 

 ton Sand have no exact analogues elsewhere ; but, as the series of 

 these Northamptonshire beds has at its upper limit and lower limit 

 respectively such definite formations as the Oxford Clay and Corn- 

 brash, and the Upper Lias, it may not be impossible approximately 

 to correlate its several members with formations in other parts of 

 the country. I have accordingly drawn up the following Table. 



