272 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 5, 



exceeding half-a-mile in radius, the various formations assume 

 positions exceedingly anomalous and complicated. On the high 

 ground of Helpstone Heath, is a large quarry in the Lincolnshire 

 Limestone ; which is exposed to the thickness of 18 to 20 feet. All 

 the beds are very oolitic, and one is very much inclined from false- 

 bedding : this is separated, by a horizontal flaggy bed, from another 

 bed as much inclined in the reverse direction. No Slate is found 

 here ; but a thin band of blue clay separates the Limestone from 

 the Lower Estuarine Sands beneath. 



Immediately north of this quarry, is Knight's brickfield. Here, 

 beneath some 10 or 12 feet of oolitic limestone, and separated from 

 it by a foot of sandy clay, are about 18 feet of the Lower Estuarine 

 Sands — in very thin and variegated layers, much inclined to the 

 north (in the direction of the neighbouring escarpment), and con- 

 taining the characteristic plant-bed in one of the upper bands. Be- 

 neath, are ironstone beds of the Northampton Sand, not exposed, 

 but probably having a thickness of 10 or 12 feet. These overlie the 

 clay of the tipper Lias, which is worked for bricks, and is at a con- 

 siderable elevation above the neighbouring low lands. A few hun- 

 dred yards to the north of the brick-pit, and at a slightly lower 

 elevation, a temporary opening, a few years ago, disclosed a very 

 solid and shelly rock of Cornbrash : a little to the south-east of this 

 point again, is the abandoned Old Coppice Green parish pit, in Lin- 

 colnshire Limestone, the beds of which are coarsely oolitic and false- 

 bedded ; while, at the bottom of the hill, at a much lower level, 

 right and left of the southern entrance to the village of Helpstone, 

 are quarries in the Great Oolite Limestone, which is surmounted by 

 a thin covering of Great Oolite Clay, with layers of Ostrea sub- 

 ruc/ulosa in a normal horizontal position. 



Half a mile further east than the Old Coppice Green pit, is the 

 most eastern point of the Lincolnshire Limestone area in this direc- 

 tion ; and about two miles further, in the parish of Marholme, or in 

 that of "Walton, is the last that is to be seen of the Limestones of 

 the Great Oolite. 



In directions, north, north-east, east, and south-east, of this 

 locality, all these Northamptonshire beds dip, and are lost, under 

 the extended field of the Oxford Clay ; which constitutes the great 

 low flat of the Lincolnshire, the Cambridgeshire, and the Huntingdon- 

 shire Eens. 



St. Maeiix's, Stamfoed. 



On the summit of the hill south of and over-looking Stamford (to 

 which I have already twice alluded), are the Marquis of Exeter's 

 excavations for ironstone, just within the Burghley Park "Wall. (See 

 PI. X. fig. 1). 



At the top of the section, in patches, answering to the surface 

 contour, appears the Collyweston Slate, weathered into slate from 

 lying so near the surface : beneath this, are the Lower Estuarine 

 Sands and Clays, having a thickness of from 6 to 7 feet, the lowest 

 band containing vertical plant-markings : immediately under these, 



