1825.] Mi: Webster s liepli/ tu Dr. Fitton. 37 



of the nature of the substances found in the places spoken of, but 

 that they are meant to apply to certain strata or beds of England, 

 which have been formerly observed, and so named by English 

 2;eolo2:ists ; the first from its containing; abundance of dark 

 green particles called green sand, and the second from having 

 in it much iron ore. 



These names, therefore, although originally given to the beds 

 with reference to their obvious general characters, are, as far as 

 this question is concerned, no more than A and B. A certain 

 bed, immediately below the chalk, and containing much green 

 sand or green earth, had been called the green sand, or A ;* and 

 another bed, situated lower down in the series than the las^t, and 

 containing nmch iron had been denominated the ferruginous or 

 iron sand, or B. Now, two beds have been subsequently 

 observed in another part of England ; I have referred the upper 

 one to A of former geologists, and the lower one to B ; but Mr. 

 Conybeare refers the lower one to A, and the upper one to 

 another bed still higher in the series, viz. the chalk marl. 



The propriety of these names have nothing to do with the 

 question, nor the opinion of any geologists respecting another 

 mode of nomenclature. They are mere names, by which we 

 distinguish these beds from each other; and indeed they are 

 highly expressive of the characters of the beds. Hud Mr. 

 Conybeare intended to state, that, in his opinion, the term green 

 sand would be more properly applied to another bed than that 

 Avhich had hitherto received it, this would entirely change 

 the view of the case; but he would tlien have alluded to tlie 

 bed which had previously been so called, and have proposed 

 the chauiie. I do not think that this was his meanins:, and 

 I am certain that he is too candid to resort to such an explana- 

 tion. 



In giving names to the beds below the chalk in the Isle of 

 Wight and tlie wealds of Surrey aud Sussex, in I811,t I followed 

 what 1 considered to be the practice of that time. We had not 

 then a geological map of England, and I c»lied them L>r<'f// and 

 ferrnginints sand, as I thought they would have been named by 

 geologists. I considered the rock of the TTuderclift" to be the 

 green sand, having in my mind the vale ofPewsey and other 

 places ; tlie bed of clay below it I called the hliie tnurl ; and the 

 whole series of beds below this I dvnom'inA ed the ferrughioin 

 sand. By the last I intended to expivss a groupj of several 



* Several oSlierbeds of England have similar grocn particles as a part of their coin ■ 

 position ; as some parts of the London clay, plastic clay, the oolites, iS:c. hut we do nut 

 for that reason call thcni green sand. 



+ See the Ta'jle at the end of my letters to Sir Henry Engleticid. 



t This practice of arranging heds first into groups I had found necessary upon seve- 

 ral occasions ; and I was the first who divided the nine huls dcscrihed by C'uvier ;ind 

 iirongniart in the basin of Paris into four groups, for the purpose of easier coii'.paiisoii 

 with thnss ah.)Vi tlie chalk in the Isle of Wight, founding this arvangenient upon ilio 

 causes that operated during the formation of tlie strata. This practice has be^ii conti- 

 nued, aiid is I'.iuiul to facilitate the study of the secondarv beds. 



