154 A Physical Description 



tions, as they are covered by a drift of sand clay and rounded 

 quartz pebbles. The paleozoic beds are regarded as connected 

 with the Silurian schists of Fingal and the west side of the 

 island. Cambrian rocks are also reported by the same 

 authority along the valley of the Tamar, on low ridges parallel 

 with the ranges, and which have been eroded by the river. 

 Silurian rocks have also been reported from the south side 

 of the island, near Port Cygnet, but I am not aware of the 

 occurrence of any fossils. 



Silurian rocks are also stated to occur in the neighbour- 

 hood of Mount JBischofF, in the north-west, but are so over- 

 laid by basaltic lava as only to be visible in a few places.* 



Devonian. — No fossils peculiar to this formation have 

 been found in Tasmania, though the period is well represented 

 in the Cordillera of New South Wales. As, however, a great 

 many carboniferous fossils are common to the Devonian 

 rocks, it is not at all unlikely that when an accurate survey 

 is made many of the rocks now regarded as carboniferous 

 will prove to belong to a lower horizon. 



Upper Paleozoic Carboniferous. — These formations are 

 so very extensively developed in Tasmania that a very long 

 list would be required to name all the localities. As a 

 rule they are exposed in alternate layers of yellow and white 

 sandstones, with shales and thin beds of limestone over 

 which again other sandstones are found. The sandstones are 

 generally firm and hard, but the limestones fall to pieces 

 very readily in some places, and in others these qualities 

 are interchanged. The dip varies, and in many localities 

 there is scarcely any dip at all, but where there has been 

 much faulting from intrusive basalts or greenstones the dip 

 is almost at every angle. No attempt has ever been made 

 to settle geologically the regular sequence of the strata 

 or to determine the horizon to which the various fossils 

 belong. Until a geological map of the east side of the island 

 is drawn after a careful survey it would be premature to 

 say anything decided from the fossil evidence, which is very 

 abundant. Coal is more or less abundant throughout the 

 island. It belongs clearly to the period of the carboniferous 

 fossils. These marine beds, as they are called, are found 

 both above and below the coal. Fossil plants are also found 

 both above and below the marine fossils. It is said that 



* "Geology of the Tin Country :" a series of very interesting letters in a 

 local paper, by S. H. Wintle. 



