112 Proceedings, 



they must have been slowly raised above the sea-level, and 

 formed dry land. Such land would come under the influence 

 of rain, snow, frost, and streams, and all the meteorological 

 agencies which tend to carve the solid land of the globe into 

 the rugged condition of hill and dale which we see ; and as 

 the land sank again the sea would finish the degrading action 

 of the rain and rivers by cutting through it horizontally, cliff 

 by clift", and so giving the surface a final levelling. 



Such was the surface on which the Gault Clay of the new 

 sea was to be deposited ; but of the intermediate land sm-face 

 we of course should know nothing ; it had been all swept 

 away by the sea. A junction of beds of this character, where 

 the upper is lying on a worn surface of the lower one, is what 

 is known as an unconformity — the beds are unconformable 

 to one another (or, as a student of Dr. Duncan's used 

 expressively to say, they are " tmcomfortable strata"). 



This break in time is further shown by the very few fossils 

 which are common to the Gault and Lower Greensand. In 

 fact, with the Gault we enter upon a new era — that of the 

 Cretaceous or Chalk Period ; for although the Lower Green- 

 sand used to be considered as a part of the cretaceous system, 

 its differences quite entitle it to be regarded as a separate 

 formation. It is now known as the Neocomian, a name given 

 to it from the locality in Switzerland where it attains its 

 largest development, Neufchatel or Neocomium. 



Though one of the minor members of the Cretaceous 

 system, the Gault attains in our district a thickness of over 

 three hundred feet, and from its mineral character we may 

 infer that when it began to accumulate a great difference had 

 taken place in Physical Geography. The nature of its fauna 

 indicates a quiet sea, rather shallow, as the cephalopods with 

 which it abounds are kinds found at no great depth. Taken 

 altogether, it may be said to be rich in fossils, though it is 

 curiously uncertain in this respect. I have not been able to 

 obtain a great variety of forms from this district, though in 

 the Lower Gault at Folkestone fossils are plentiful enough. 

 It is true that there we get the Gault beautifully exposed in 

 the cliffs, and about here good sections are scarce. I asked a 



