Strata between Durlstone Head and Old Harry. 85 



He goes on : — " It is for theorists to identify these beds 

 with what are called Hastings sands." Theory is, surely, a 

 most illogical way of identifying one thing with another ; and 

 it is not by theory, but by an actual comparison of the fossils, 

 which Dr. M. says " he has never heard of" (!) as well as 

 by the miner alogical character, that the identity with the stra- 

 ta at Sandown Bay, Isle of Wight, has been made out. He 

 will find there precisely similar beds of yellow and brown 

 sand. As to the term, theorist, it can only apply to one who 

 would class beds between the chalk and the wealden strata, 

 with the sands of Alum Bay, or, "what is more," with those 

 over the London clay ! In the first place, I may observe, the 

 sands at Alum Bay, are not opposite to Swanwich Bay. — 

 Alum Bay is opposite to Studland Bay, and Swanwich Bay 

 is opposite to the east side of Freshwater Bay, on the other 

 side of the Isle of Wight. The chalk, in each case, separates 

 the plastic clay from the sub -cretaceous beds. In the next 

 place, mineralogical character alone is but of little avail, in 

 many cases, as a geological test. I could shew, from my 

 own collection, specimens from the ascent to Fairlight Down 

 near Hastings ; the plastic clay of Dorsetshire ; the quarries 

 in the Gres Bigarre at Liverpool ; and from the old red sand- 

 stone near Huy, in Belgium ; which so exactly resemble each 

 other, that no eye could detect whether they belong to one 

 or to four formations ; and every geologist, who has exten- 

 sively worked out his own acquaintance with rocks, knows 

 well, that mineralogical character is most deceptive. Mr. 

 Lyell, (Principles, 5th ed. vol. iv. p. 148), speaking of the 

 tertiary fresh water deposits of Auvergne, says that there are 

 beds of " red sandstone and red marl, which are identical, in 

 all their characters, with the secondary new red sandstone and 

 marl of England. In these secondary rocks, the red ground 

 is sometimes variegated with light greenish spots, and the 

 same may be seen in the tertiary formation, of fresh water 

 origin, at Coudes, on the Allier." I am able to confirm, from 

 examination, Mr. Lyeli's remark ; as strongly I deny, from 

 examination, Dr. Mitchell's position, that the sands of Swan- 

 wich Bay " are not to be distinguished from some of the per- 

 pendicular strata directly opposite, ( ? ) in Alum Bay" I have 

 now before me, bottles filled with sand from both localities. 

 I can see a material distinction in the character, — mineralo- 

 gically, however, they agree in both being quartzose, and 

 both coloured by iron I Is this sufficient for a geologist, and 

 one who criticises others upon such grave topics as the pro- 

 per classification of strata ? It ought not to be, most assur- 

 edly. 



