310 Rev. W. Doicnes — A Section near Honiton, Devon. 



But independently of the diagram, there was a certain balance of 

 other improbabilities which had to be weighed. It was improbable, 

 as urged by Mr. Ussber, that the Bhastic beds should attain so great 

 a thickness, — about 160 feet. It was improbable, as urged by Mr. 

 H. B. Woodward, that they should locally assume an arenaceous 

 character (though, as already mentioned, the beds in question are not 

 arenaceous throughout). But on the other hand, it was improbable 

 that the marked unconformity, usual between the Trias and the 

 Greensand, should be absent in this one spot, that the Trias should 

 have in this particular spot no proper dip whatever, but should 

 acquire just about its normal dip abnormally through the downthrow 

 of a fault, and should exactly share that dip with Cretaceous beds 

 above it. 



Again, it was antecedently most improbable that Gault-like rock 

 should reappear in this locality. At Lyme Begis, 25 miles to the 

 S.E., black marl with Lima parallela occurs, but this appears to be 

 approaching extinction westward, and is there only about 20 ft. thick. 

 At Uplyme, Trinity Hill, Shute Hill, and Dalwood Down, eminences 

 in a straight line from Lyme Begis to Honiton Tunnel, along the 

 line of dip no Gault is found. And we seek for it equally in vain 

 along the line of strike. Yet at Honiton tunnel something of the 

 nature of Gault is found. 



It would seem that to connect these Honiton beds with the Lyme 

 Begis bed, a curved line must be drawn southwards and passing out 

 to sea. Traces of dark grey beds, — all however arenaceous — are 

 seen in the cliff-section at Whitecliff and at Seaton. Further out to 

 sea there might once have been an areno-argillaceous bed connecting 

 the 20 ft. bed of Lyme Begis with the 6 ft. bed of like character at 

 Honiton. It is a conjecture with at least some probability about it. 



But when we compare these so-called Gault beds of the West 

 with the typical Gault of Folkestone (Quantum mutatus ab illo!), 

 what have they in common ? The argillaceous character has been 

 almost entirely supplanted by an arenaceous one. The fauna has 

 undergone many modifications. Lima parallela still lingers on in 

 the attenuated bed at Lyme Begis, but has not yet been found at 

 Honiton, where the semi-argillaceous bed is still more attenuated. 

 Even the colour gets washed out as we go westward. Clay merges 

 into sand. Black merges into yellow. In a word, between Upper 

 Greensand and Gault boundary there is none in the West of England. 



With the exception of the unconformity represented in the upper 

 beds of the section, the diagram in the possession of the L. & S. W. 

 Bail way is no doubt mainly correct. It gives the following thick- 

 nesses to the several beds : — 



Clay with Chert passing into Cherty Greensand, hedded ... 55 feet. 

 Grey Sand 81 



Yellow Sand 



Varigated Marly Clay 



Black Sand 



White Sand 



Greenish Sandy Clay 



... 18 „ 



.. 6 „ 



.. 44 „ 



.. 1 „ 



.. 10 „ 



215 ft. 

 Red Marl. 



