195 



Blue Lake depression. R. A. Daly < 2 °) has subsequently dis- 

 cussed the term "caldera," shown to what varied uses it has 

 been put by different writers, and prefers to apply the word 

 to explosion forms only. His term "volcanic sink" hardly 

 fits the case of Blue Lake, and it is probably best to refer. 

 to it in simple English as a "collapsed crater." 



(c) The Leg of Mutton Lake. — This is a small, steep- 

 walled depression. The sides are covered with soil and clothed 

 with native and introduced trees, in striking contrast to the 

 bare rock walls of the Blue Lake. One of the nurseries of 

 the State Forestry Department nestles picturesquely at the 

 bottom, alongside the lake. Brown's section suggests that the 

 depth of this lake is about 70 ft., but it looks much shallower 

 than that. Woods called this the Centre Lake; it has since 

 received the present name from its shape. The depression is 

 deep enough to show both the limestone and the basaltic 

 layers, but they are apparently quite covered over with 

 volcanic material that has slumped down or been washed down 

 from above (see fig. B, pi. x.). 



(cl) Valley Lake. — This name was applied by Woods to 

 both the present lake and the Crater Lake, which are con- 

 nected by a shallow channel when the water is high, and dis- 

 connected when the water is low. The Valley Lake, as may 

 be seen in fig. 6, is steep-walled, with good sections, on the 

 east and north. The extent and nature of the collapse is 

 comparable with that of the Blue Lake, and the water has 

 the appearance of great depth. There is no definite record 

 of the systematic sounding of any of the lakes except Blue 

 Lake. The western wall is almost non-existent, and the 

 southern wall is low and gently sloping. Down this southern 

 wall a road has been constructed for tourist purposes. 



On the peninsula, separating Crater Lake from Valley 

 Lake, there are two or three funnel-shaped depressions, pos- 

 sibly due to small local subsidences. W'oods regarded them 

 as small craters. 



The two irregular peninsula shapes that jut into this 

 depression, partly separating the Crater and Valley Lakes, 

 are probably due to the much greater amount of tuff that 

 was here concerned in the subsidence (see fig. 7). 



(e) Crater Lake (also called Browne Lake). — Excepting 

 the Leg of Mutton Lake, this is the smallest, and apparently 

 the shallowest, of the group. Mr. E. F. Crouch, of the Old 

 Residents' Association, Mount Gambier, informs me that 

 when his parents came to Mount Gambier, in 1841, this lake 



(20) Igneous Rocks and their Origin, R. A. Daly. New York, 

 1914 (pp. 144-6). 



