IX AU G URAL ADDRESS . 
3 
Laurentian, Cambrian, and Silurian, did not extend far from the 
eastern islands, and are principally developed in Queensland to the 
north and in Victoria to the south, but, being of marine formation, 
they did not then materially affect the geographical configuration, 
though they are important features of the present time, and are the 
chief sources of our tin mines ; and silver, lead, and copper also exist 
in sufficient quantity to afford prospect of future industrial success. 
There is also a marked characteristic in the abundant occurrence of 
fluor spar, which is an exceedingly rare mineral in the later formations, 
while gold does not occur in important quantity except in its upper or 
Silurian strata in Victoria. Near Zilmantown (lat. 17 deg. 20 min. 
S., long. 144 deg. 30 min. E.). there are interesting developments of 
these rocks, which now form steep ranges with Hat-bottomed valleys, 
in which coralline limestone, of the Devonian period, rests unconform- 
ably, and in places rises abruptly several hundred feet, presenting the 
form of ancient coral reefs, such as now exist on the Great Barrier 
reefs. In fact, they indicate that at some remote time a passage 
existed from the east coast to the southern part of the Gulf of Car- 
pentaria, under similar conditions to those of the present Torres 
Straits, and that the subsequent elevation of the land has now placed 
it more than 500 feet above sea level. This description of the present 
state of these rocks is, however, a digression in regard to geological 
sequences of the early period. 
FIRST APPEARANCE OF ORGANIC LIFE. 
The Cambrian and Silurian period was succeeded by the Devonian, 
during which there is little evidence of any great variation in the 
limits of the sea and land, hut organic remains show that the conditions 
were becoming more favourable for the development of marine life. 
The rocks consist principally of fine-grained slates, which must have 
been deposited in a deep sea, and in some places the now visible 
sections indicate a thickness of 10,000 feet. 
The upper strata connected with the Devonian series have been 
classed by geologists as belonging to the Permo-Carboniferous, on 
account of the marine fossils which have been found in the Gympie 
series of rocks. Some difficulties, however, arise in regard to the 
identification of Australian rocks with those of Europe on the sole 
basis of the occurrence of nearly the same species of mollusca, and it 
may be remarked that in Central North America the appearance of 
fossil mollusca and plants which would in Europe indicate a definite 
position of strata, often occurs in rocks which lithologically and 
stratigraphically are of an earlier date ; and the same conditions of 
the earlier appearance of species and genera seem to obtain in 
Australia, and if ultimately established would clear away many of the 
existing difficulties in the comparison of Australian and American 
fossils with those of Europe. Accepting the classification of the 
