1866.] the Western Himalaya and Afghan Mountains. 199 



o +- 



fe OS 



a 



Masses, Beds, &c. &c. 



Fossils. 



Condition indicated. 



Fauna changes. 



a. Dark, blue or black ar- 

 gillaceous limestone. 



b. Slate and shale. 



c. Sandy limestone with- 



out fossils. 



d. Shales; sandy Bbales: 



clay iron-ore in ribbons 



e. Limestone like a; pass- 

 ing into calcareous 

 slates. 



Thickness = 500 feet. 



ropoda 

 and Cyatho- 

 phylUda. 



None. 



Oa8teropoda 



and Cyatho- 



phylUda. 



Protected creeks,rathor swampy. 



Rivers bringing down mud to a 

 shallow sea. Sublittoral oscil- 

 lations. 



Drift on shallow shelving coast. 



Shelving low land near sea- 

 shore, traversed by rills from 

 hot chalybeate springs. Sub- 

 littoral oscillations. 



Shallow creeks or protected sea 

 coast. Swamp with grasses? 

 Shallows between tides ? 



This succession of beds shows a steady shallowing of the sea. If 

 we reflect for a moment how the sea bottom which received the 

 limestone was formed, by volcanic ash and ejecta falling into the 

 sea around the craters of numerous volcanoes, we would be led to 

 expect a shallow shelving sea coast. Whether the volcanoes had 

 existed for ages and prevented the development of life during the 

 Silurian epoch, or whether they broke out after the Silurian beds 

 had been deposited and buried these beds under their ejecta, I 

 cannot say. It appears much more probable however that the volcanoes 

 existed during the Silurian epoch, and prevented marine animals 

 from living, by keeping the water at such a temperature or per- 

 meating it by such gases as were incompatible with life. However 

 this may be, there can be no doubt that the volcanic ejecta were 

 disposed in very gently sloping beds all around the volcanoes which 

 produced them, and, as these ejecta were arranged by water, we would 

 naturally expect the beds they formed to extend far into the sea. 

 Hence a long shelving shallow coast would be formed, a coast which 

 would speedily become more and more shallow from the enormous 



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