1866.] the Western Himalaya and Afghan Mountains. 199 
hot chalybeate springs. Sub- 
littoral oscillations. 
a 
0 
& = Masses, Beds, &c. &c. Fossils. Condition indicated. 
i 
FAUNA CHANGES. 
(a. Dark, blue or black ar-| Gasteropoda |Protected creeks,rather swampy. 
gillaceous limestone. jand Cyatho- 
phyliide. 
¢ | \0. Slate and shale. None. Rivers bringing down mud to a 
a shallow sea. Sublittoral oscil- 
| lations. 
a | 
e. Sandy limestone with- aasien Drift on shallow shelving coast. 
S) out fossils. 
a 
@ | \|d. Shales; sandy shales;|} ...... Shelving low land near sea- 
| clay iron-ore in ribbons. shore, traversed by rills from 
e. Limestone like a; pass-] Gasteropoda |Shallow creeks or protected sea 
ing into calcareous|jand Cyatho- | coast. Swamp with grasses P 
slates. phyliide. Shallows between tides ? 
_ |Ehickness = 500 feet. 
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 
25 
