58 



able example in my possession, obtained when the present 

 road down to the bottom of the crater was being cut, shows 

 a finely laminated sedimentary deposit, thickly covered on the 

 faces of the laminse with vegetable impressions. The deposit 

 is evidently a recent one, and has become hardened, rendered 

 fissile, and the vegetable matter carbonised by the heat. In 

 addition to the sand, which makes up so large a proportion 

 of the "ash'" beds, there occur in some parts of the inner face 

 of the cone a fair number of small waterworn quartz pebbles, 

 ranging up to the size of a marble, which it is difficult to 

 account for except on the supposition that they once formed 

 part of a lake beach, or small shingle of a running stream, that 

 occupied the site of the extinct volcano."^ 



Mount Schank. 

 This volcanic cone, which rises abruptly from the plain and 

 forms a striking feature in the landscape, is about eight miles 

 south of Mount Gambier. The Rev. Tenison Woods described 

 Mount Schank as possessing two vents, an older and much 

 wasted cone, and a newer vent, which had formed on the 

 northern rim of the older crater, the newer vent constituting 

 the main Mount of to-day. Mr. Woods has, I think, en- 

 tirely misunderstood the features of the mountain in this 

 respect. All the appearances indicate that the ejected mate- 

 rial, which has built up the Mount, has come from the same 

 vent. What Mr. Woods regarded as an older crater is a 

 depression caused by the subsidence of the walls of the crater 

 on its southern side. This appears to be the case from the 

 following consideration : 



{a) The fracture of the walls in the so-called "older crater" 

 is perfectly sharp in outline, and the face has not been 

 obscured in any way by showers of ash, which, on Teni- 

 son Woods' theory, »must have been scattered over the 

 base of the mountain, and more or less obliterated the 

 outline of the older crater had it existed. 

 (h) The rim of the "older crater," instead of being quaqua- 

 versal in its dip, as viewed from its centre, is seen to 

 make a symmetrical curve passing upwards to the sum- 

 mit of what is regarded, in Tenison Woods' theory, as 

 the "newer vent," proving that the latter has been the 

 source of the ejected material. 

 {c) The segment of the crater, where the subsidence has taken 

 place, has a greater steepness than other portions in the 

 external slope of the cone, and is concave in outline. 



* It is possible that the sand and small shingle which are found among 

 the ejected material may have had their origin from the breaking up o* 

 friable Tertiary sandstones within the limits of the vent. 



