160 THE VICTORIAN NATURALIST. 



From the low dips and the distinct stratification it is probable 

 that the materials were deposited in water. Mr. Selwyn suggests 

 low islands in the sea. It may be noticed, however, that strati- 

 fication of the tuffs does not necessarily imply deposition in water, 

 and that low dips may in some cases be due simply to the fact 

 that the accumulations had not yet sufficiently raised the level 

 near the vent to give a high dip. If, indeed, we regarded what is 

 now seen as derived from the lake as a vent, such would be highly 

 probable, for the small thickness of tuff, with observed dips, would 

 run out a width small compared with the size of the crater. 

 Deposition on an inclined surface may account for an anomalous 

 dip of the tuff as at Murray Brook, south-west of the lake. It 

 seems, however, much more probable that a vent of this size is 

 the shattered base of a hill of once much greater elevation and 

 more normal proportions. 



On my return from Tower Hill I spent one day at Allansford. 

 Lake Wangoom, 3 miles from Allansford, on the west side of the 

 Hopkins River, seems also probably an explosion crater lake. 



NOTES TO MAP OF TOWER HILL. 



The horizontal shading shows the position of outcrops of the underlying 

 Lower Tertiary Rock. 



Q. — Positions of Quarries. 

 S. — Springs. 



A. — Road cutting where the largest basalt block was seen. 

 The edge of the deep water area is marked by a dotted line. 

 On the Island — 



C. — Most perfect Craters, with pools at the bottom. 

 V. — Old Crater at high level. 

 X. — Probable other Craters. 

 The positions of these craters and their dimensions, also the heights, are 

 only approximate. 



The section illustrates the relation of the ash and tuff, and the central 

 accumulations forming the island, to the Lower Tertiary Rocks. 



THE TUFFS OF LAKE BURRUMBEET. 



By T. S. Hart, M.A., 

 Lecturer on Geology, School of Mines, Ballarat. 

 ( Read before the Field Naturalists' Club of Victoria, 10th September, 1900.) 

 Lake Burrumbeet is situated about 14 miles west of Ballarat. 

 It extends four miles in a north and south direction and about 

 three miles in greatest width, and has an area of about 5,200 

 acres. It is said not to be deep. The water supply is chiefly 

 from the Burrumbeet or Bo-peep Creek, which rises north of 

 Ballarat, and enters the lake near the south-east corner. The 

 overflow of any surplus water is nearly opposite to this, to Baillie's 

 Creek and thence to the Mt. Emu Creek, the chief eastern 



