1850.] AUSTEN— SANDS AND GRAVELS OF FARRINGDON. 471 



surface of the oolitic sea-bed prior to the deposition of the gault over 

 Oxfordshire, Berkshire, and Wilts. 



There are other considerations which warrant the assertion that 

 the superposition of the gault on the ironsands at Devizes is of no 

 value whatever, in the shape of proof of the sequence and connexion 

 of the two deposits. 



The oolitic deposits in their range into the South of England gra- 

 dually acquire a north and south direction, and this disposition dates 

 back to a period before the cretaceous, inasmuch as this latter series 

 in its extension westwards overlaps in turn every member of the 

 oolites : the two series may be represented by two converging lines 

 or bands, which at length meet ; but the order of succession pre- 

 sented at such point of meeting can no more prove the continuity of 

 the gault with the ironsands as parts of one system of deposits, than 

 it can with any portion of the middle or lower oolites with which it 

 afterwards comes in contact. The position of the gault on the Far- 

 ringdon beds at Devizes is clearly transgressive, and can only show 

 that the latter are not newer than the gault (or of the age of the crag), 

 which for anything to be seen at Farringdon might be the case. 



From what has been here stated, as to the composition and posi- 

 tion of the Farringdon and equivalent beds, it will be easily con- 

 cluded, by some, that they must be either Portland or lower green- 

 sand, and if not one, then certainly the other. 



One very apparent defect in the geological investigations of the 

 present day, is the disposition to adjust each successive addition of 

 knowledge to a certain artificial scale of formations ; and of this ten- 

 dency geology must free itself, if it would arrive at the true nature of 

 the physical changes with which it is concerned. The artificial 

 scale of formations, which still figures in elementary treatises, more 

 particularly with respect to secondary geology, represents an order 

 of superposition, and lines of separation, which are both untrue, as 

 well with respect to the mineral masses as the forms they contain — 

 the result of the too hasty generalization of local phsenomena. The 

 Farringdon beds seem to present an instance of what some of the 

 steps may be in the progress of change from one series of formations 

 to another. 



If the Farringdon beds were non-fossiliferous, we should arrive at 

 their age by such considerations as these : — that they occur at, and 

 are connected with, the top of the Kimmeridge clay, and that they 

 never occur in any other position — in which respects they coincide 

 with the Portland deposits ; that the lower portions of both consist 

 largely of conglomerates, composed of peculiar materials ; that the 

 upper part of the Portland contains indications of a contemporaneous 

 area of fresh water, as apparently the ironsand does at Shotover ; that 

 their denudation was effected before the period of the gault. On 

 these and other common features, each of which is the evidence of 

 distinct physical changes and operations, the which could hardly 

 have taken place in the like order at two distinct periods of time over 

 the same spot, we should be warranted in considering the Farringdon 

 beds the equivalents of the Portland. I will not however press this 



