98 [Proc. B. N. F. C, 



Pecten, Lima, Terebratula, and Rhynchonella are abundant. 

 These sandstones pass up into (2nd) hard white limestone of the 

 chalk formation. This is, as a rock, unique in the British 

 Islands, notwithstanding the fact that it is chemically the 

 equivalent Of the English chalk, aud only differs geologically 

 by being slightly younger. This limestone, or hard chalk, was 

 formed in a deeper sea, the most characteristic fossils found in 

 it being its belemnites, conico-cylindric bodies which were the 

 internal axes of ancient cuttlefish. The formation of the flints, 

 so abundantly arranged in layers in our chalk rocks, has been 

 the subject of much discussion ; that they originated in sponges 

 which flourished in the ancient cretaceous seas seems, however, 

 most probable. That the chalk itself was built up by innumer- 

 able aggregations of the shells of animals of microscopic dimen- 

 sions can be demonstrated by a lens of moderate power applied 

 to a sufficiently thin slice of rock. 3rd. The elevation of the 

 ancient sea-bottom, its consolidation into the hard rock we now 

 find, and its subsequent long-continued erosion, which is 

 nowhere better seen than in the Whitewell quarries. The once 

 level sea-bottom has been worn into an irregular surface, having 

 in places deep hollows or pockets now filled up with loose flints 

 that have resisted the force of decomposition which wore away 

 the chalk rock. A section at the northern end is peculiarly 

 instructive— a confused mass of angular blocks of limestone lies 

 up against a vertical cliff of the same rock. This is evidently 

 the effect of ancient erosion, as the basaltic lava has been poured 

 out equally over the limestone debris and the limestone in 

 place, the interpretation being that this limestone debris is the 

 talus ox undercliff of an escarpment which existed in early tertiary 

 times. 4th. The eroded surface of the chalk, then covered 

 with heaps of loose flints, was overflowed by lava welling up 

 from the innumerable crevices which we now find filled with 

 trap rock, and which are known to geologists as dykes. There 

 were, no doubt, several of these outflows, and the once plastic, 

 but now indurated mass, forms the massive rock known as 

 whinstone. In the absence of the secretaries no formal meeting 



