2115 
THE GEELONG NATURALIST. 
forming a septum, making a complete cell; and 2nd,—How the 
cell grows. 
. At the conclusion of the lecturer's remarks, Mr. F. R. Pincott, 
moved, scconded by Mr. W. Shaw, that the best thanks of the Club 
be accorded to Mr. Tisdall for his highly interesting and instructive 
lecture. The motion on being put was carried with acclamation. 
Mr. Tisdall briefly acknowledged the compliment, and has kindly 
promised to give another lecture at an early date. 
* THE AGE OF BASALTS AROUND GEELONG. 
Bx Mr. J. F. MULDER. 
Read before the Geelong Field Naturalist Club, September 10th, 
1895. 
Tux Geology of the Valleys of the Moorabool, Leigh and Barwon 
Rivers, with the flat lands extending between the Cape Otway 
Ranges, Barrabool Hills and Waurn Ponds, indicates that these 
depressions were originally formed by ocean currents. 
These currents appear to have washed away great masses of 
the older secondary and other rocks, causing such valleys as those 
of the Moorabool and Leigh. ‘Thesé valleys and depressions were in 
turn filled up with the skeletons of corals, shells and bones of fish 
such as sharks, and thus was formed the limestone rock. This 
limestone is of early Eocene age, there being less than 2 per cent. 
of living shells found in it, and it is found all over this district. 
The depth of the sea in which this deposit was formed was 
. probably from 40 to 60 fathoms and upward, as itis found that 
that is about the depth that corals thrive best in at the present 
day. 
In this district the limestone lies, in most cases, directly on 
the older rocks. For instance at Waurn Ponds on the right hand 
side of the Colac Road in the bottom of the creek it is freestone 
(Mesozoic,) but the hill beside it is limestone of the district 
Again up the Moorabool valley you have it overlying the granite, 
while at Curlewis and Eagle Rock it rests on the Eocene basalt. 
At Curlewis I know that at present the blue fossil clay lies on the 
basalt, but that faet is easily disposed of by supposing that the 
limestone was washed away before the clay was deposited. The 
same process is going on now around our coast-line. The ancient 
softer formations are being washed from the harder underlying 
rock, and the forms of life existing now are being put in their 
place mixed with mud and silt. The limestone underlies the fossil 
clay. This we know is the case, for in the shaft sunk at Belmont 
the men had to sink through the fossil bearing clays to reach the 
* For Diagrams relating to Basalts see page 20. 
