^4 Proceedings of the Royal Society of Victoria. 



thick, but at a lower level than that of the surrounding plains. 

 Many of the small spurs jutting on to the flats from the main 

 bank have small basaltic outliers on them, at a level about half 

 way between the river-bed and the table-land. This basalt is 

 evidently not interstratified with the beds of Miocene (Eocene) 

 age ; it would therefore appear that a depression in the latter 

 had been filled in by the basalt, forming a thin capping, and that 

 the river, in cutting its course, took the line of this depression, 

 leaving occasional mounds and spurs from which it failed to 

 remove all the basalt, as, from its more durable nature, it 

 protected the beds on which it rested." 



It may be added that there is a fragmentary drift, consisting 

 of quartz pebbles from the size of a walnut downwards, on the 

 lava of Dog Island. Below the lava eocene limestone shows in 

 places, but only where the surface soil has been disturbed. This 

 again rests on the ordovician. The summit of the knoll is 130 

 feet above the river, while the main bank is about 110 feet 

 higher. The latter is capped by the upper basalt ; just beneath 

 this, and therefore at a high level, there are several conspicuous 

 outcrops of massive limestone similar to those at the amphi- 

 theatre. 



To trace the lower basalt continuously down the river will 

 require some detailed plotting, which we have not yet found 

 time for, and at present we cannot pretend to do more than give 

 a rough outline. We have already recorded that just south of 

 Dog Island a small outlier appears on the opposite or western 

 bank, with only 35 feet between its base and the level of the 

 water. Rocky Castle, which is 85 feet high, is close to this spot. 

 Still keeping on the right bank, the old lava stream, or, to speak 

 more correctly, that remnant of it we followed, at last strikes 

 the river at the southern end of Henderson's Flat, where it 

 becomes conspicuous as the bold bluflf of Point Henry. From 

 here the stream has evidently cut its way I'ight through the lava, 

 as this now shows on both banks. The eastern branch terminates 

 within a short distance of Golf Hill, but the western continues 

 on until it finally runs out about a mile and a half below Shelford. 



The present thickness of the lower basalt of course varies 

 greatly according to the amount of erosion it has suffered. At 

 Dog Island, the Survey gives it as 10 feet ; at Point Henry it is 30 



