AND THEIE EXTENSION IN HEETFOEDSHIEE. 163 



the Geological Society,' vol. xxii. p. 414, and the result of his 

 observations may be summarized by a table thus : — 



As we travel westward from the neighbourhood of Ramsgate, the 

 formation becomes less diversified, and between the Medway aud 

 London only two of the five divisions are found ; these are a and c, 

 the latter of which has increased to a veiy considerable thickness, 

 60 feet in some places, and forms the typical Thanet Sand. Very 

 good sections of the bed may be seen at Charlton, near Woolwich, 

 and lower down the river at Erith, where the sand has been ex- 

 cavated for a long period of time to serve as ballast for Tyne- 

 returning colliers, and afterwards to do duty for casting purposes 

 at the great iron works of the north of England. Its fitness for 

 casting operations is due to its soft loamy character, which is so 

 marked that it is called by the men who work it not sand but loam. 

 Thick as is this bed, and extensively as it has been worked for 

 many years, only a doubtful cast of a Pholadomya has been found 

 in it. The bed d, however, at several places — Pegwell Bay, near 

 Heme Bay, etc. — is very fossiliferous, one species especially being 

 most abundant ; this is the Cyprina Morrisii, which is found in a 

 beautiful state of preservation. Other species in the Thanet Sands 

 are Astarte tenera, Corhula regulliensis, and Pholadomya Konincki. 



Though the Thanet Sands of England have a very limited ex- 

 tension, and are not found at all in the Hampshire Basin, they are 

 not confined to this country, but are met with in Belgium on the 

 east, and in France on the south of the Channel, where they are 

 called Sahles de Bracheaux. From the character of the fauna it 

 has been inferred that the Thanet Sands sea was' a comparatively 

 cold one, considerably colder than the sea which succeeded it. 



Climatal conditions in various parts of the world at the present 

 time show that places in the same latitude may have very different 

 temperatures. The British Islands enjoy a much milder climate 

 than the lands on the west of the Atlantic equally distant from the 

 pole. This is doubtless caused to a great extent by the con- 

 figuration of the land on the globe, the central part of the 

 American continent deflecting the great equatorial current, and 



