420 PURBECK BEDS AND IRON -SAND. CHAP. 



thicker beds, in all 7 ft. 8 in., and then 6 ft. of loam, and I ft/ 8 in. 

 of hard blue stone with spiral shells, and water. If these be taken 

 for Portland rock, all the layers above may safely be regarded as 

 representing the Purbeck series. Above them lie various coloured 

 sands, red, white, and brown, and these are occasionally cemented 

 into pebbly rock. These may be seen in the hill above Stone. 

 One section reads thus : 



Pebbly rock. 



Yellow sand. 



Irony and pebbly sand, with wood. 



White clays. j 20 to 30 feet. 



White and yellow clays and fuller's-earth. 



White sand. 



Striped yellow and pebbly sand. J 



This is obviously of the same series as the iron-sands of Shotover, 

 which are of greater thickness and yield more abundant evidence 

 of fluviatile affluents. 



Similar facts occur at Whitchurch in Buckinghamshire. 



Thus the iron-sand of Shotover is connected with the more ex- 

 tensive deposits of Buckinghamshire and Bedfordshire; and the 

 ancient generalization of Holloway, who united in one deposit the 

 sands, ochres, and fuller's-earth of Woburn and Shotover, is con- 

 firmed. 



Smith, who regarded these sands as of the same great group as 

 the Hastings sands in this agreeing with Conybeare records the 

 occurrence, at Steppingley Park, near Woburn, of gault over the 

 sands, and containing its characteristic ammonites. Thus we find 

 the ' iron-sands' to be inferior to gault, and superior to Purbeck 

 beds ; they may at present, with much probability, be referred to 

 the Hastings sands; it is, however, possible that they may be 

 an estuarine deposit of the lower greensand age. 



It is to be hoped that the Geological Survey, in its progress 

 to the north-east, will furnish new data, and especially additional 

 evidence from organic remains, for the determination of the phy- 

 sical condition of this region in the later oolitic; period. I regard 

 it, however, as certain, that much of the so-called ' iron-sand' on 

 the northern outcrop of the London basin must be ranked among 

 estuarine deposits. 



At the present time it can hardly be said that true iron-sands 

 occur in the range of country west of Oxford, nor is there much 



