76 THE VICTORIAN NATURALIST. 



Quarry, Berwick, they overlie a deposit containing numerous 

 fossil leaves, which seems to have been still in progress at the 

 time of the lava flow. To the south they pass under Tertiary 

 deposits, and may be continuous with the basalt found under 

 200 feet of Tertiaries at Mordialloc. 



We thus see from the sections round Melbourne that there is a 

 series of older volcanic rocks overlaid by marine Tertiaries, and 

 perhaps a second series before the Newer Volcanic. The age of 

 the first series of volcanic rocks has been put down as the close 

 of the Miocene, the Tertiaries overlying them being regarded as 

 Pliocene. But Messrs. Hall and Pritchard have recently shown 

 (" Proc. Royal Soc. of Vic," vol. ii., N.S.) that the Eocene strata 

 at Bellarine rest on the denuded surface of similar volcanic rocks, 

 and in other localities also the same relation exists. Further 

 palasontological examination of the Tertiaries round Melbourne 

 also tends to assign to them an earlier age. 



Coming now to the Newer Volcanic rocks, we find that for the 

 most part they form open plains with a shallow soil, and 

 frequently very stony. The rock is for the most part basalt, 

 varying in colour and texture at different places. It may be seen 

 in section along most of the creeks and rivers in the plains, 

 sometimes to a thickness of 100 feet; but over the old valleys it 

 may often be much thicker. Points of eruption are very 

 common, mostly in the upper parts, the nearest to Melbourne 

 being one to the north-west of Somerton station, on the North- 

 Eastern line. The lava streams have filled in the valleys, and 

 have sometimes covered the hills dividing them. By this the 

 drainage system of the country has been considerably modified. 

 When a valley has been partly filled by a lava stream, it 

 frequently happens that the river has cut out a new course along 

 one side, the Silurian rocks being more easily denuded than the 

 basalt ; many instances of this occur. The Yarra occupies the 

 boundary line between the basalt and Silurian from Alphington 

 to Prince's Bridge, the basalt only once crossing to the left side of 

 the river, at Hawthorn. The Saltwater above Sunbury, and the 

 Deep Creek in the parish of Darraweit Guim, are other examples. 

 The upper parts of each of the valleys as a rule contain several 

 points of eruption — though it is not always clear how much of 

 the basalt is due to each — and from these the basalt has flowed 

 over the plains. In the upper parts of the Merri Creek there 

 are seven points of eruption recorded in the quarter sheets. In 

 one of these, Beveridge Hill, there is a distinct though much 

 worn down crater, with a swamp in it. On one side there is a 

 cutting in ash and scoriae, near the Sydney road. Down the 

 middle of the Merri Creek valley there is a line of inliers of 

 Silurian rock which probably mark an old division of the valley 

 into two. On both sides of the volcanic area there is a line of 



