170 



1. Introduction. 

 Mount Gambier is situated in the extreme south-eastern 

 corner of South Australia. The volcanic features of that 

 district, of which Mount Gambier is the most important, mark 

 the western limits (D of that great area of comparatively recent 

 volcanic activity that affected the greater part of central and 

 south-western Victoria. 



The cinder cones of Mount Gambier were never large, nor 

 is the area covered by the ash deposits of very great extent. 

 The volcanic phase was accompanied or followed by extensive 

 collapse of the greater part of the area covered by the cones 

 of ejected material, so that only remnants of the original 

 cones now mark the points of activity. The areas of the col- 

 lapse are now occupied in part by deep lakes. 



Several factors combine to make Mount Gambier of special 

 interest. The fertile volcanic soils are of great economic 

 importance, and because of them the town of Mount Gambier 

 has grown up, and has become the chief business centre of 

 that portion of South Australia. The "Mount," with its 

 beautiful lakes, being the product of two series of catastrophic 

 happenings, namely, a rapid volcanic up-building, with sub- 

 sequent extensive collapse, presents scenic features of an 

 exceptional nature and of great variety and beauty. From 

 the scientific point of view, the structural features present 

 special facilities for investigating the mode of origin of the 

 present physiographic features. 



The observations on which this paper is based Were car- 

 ried out in such leisure hours as were available during 

 numerous visits to Mount Gambier, extending over the past 

 five years. In this work the writer has received invaluable 

 and enthusiastic assistance from Mr. H. C. Hosking, B.A., 

 of Mount Gambier, to whom his best thanks are due. The 

 writer is also indebted to Mr. L. Keith Ward, B.A., B.E., 

 Director of Mines, South Australia, for his assistance and 

 suggestions. 



2. Discovery and Settlement of Mount Gambier. 



On the evening of December 2, 1800, Lieut. James Grant, 

 on a "voyage of discovery" in the "Lady Nelson," was near- 

 ing the coast in the neighbourhood of Mount Gambier. So 

 far the navigator had not sighted Australia, but a close watch 

 was ordered to be kept for signs of land. The first such sign 



(i) With the possible exception of the Kangaroo Island basalts 

 (see "Enstatite Basalt from Kangaroo Island, South Australia," 

 E. R. Stanley, Trans. Roy. Soc. S. Austr., vol. xxxiv.. 1910, 

 p. 69). 



