38 PROCEEDINGS OF THE GEOLOGICAL SOCIETT. [Nov. 20, 



3 feet on the average, wherever the diluvium of loam and clay 

 has been removed by fluviatile agency. This deposit has been 

 made by numerous floods of this nature. At such a time the channel 

 is considerably altered — cutting away its bank on one side, and de- 

 positing material on the other. In this way the rivulet may be 

 said to have travelled backwards and forwards through ages, ever 

 rearranging the old rounded material. The period, however, required 

 for these changes may be faintly conceived by the fact that in many 

 parts there are 20 feet of Tertiary drift reposing on this bed of 

 rounded stones. This fact has led some intelligent colonists to 

 regard these rounded stones as indicating the bed of an ancient river. 

 Wherever a rivulet, taking its rise from the mountain-regions in 

 this island, disembogues its waters, a similar deposit of rounded stones 

 is to be seen. At Sandy Bay, for instance, only two miles from this 

 city, at the mouth of a rivulet, such a deposit is seen covered with com- 

 minuted shells of recent species to a depth of from 8 to 10 inches ; and 

 these again are overlain by two or three feet of vegetable soil*. 



At the springs on the south-western side of Mount Wellington 

 there are evidences of just such another landslip having taken place 

 in former times. Here the side of the mountain has about the same 

 angle as that at Glenorchy ; but the altitude is somewhat greater at 

 this spot, which is now densely timbered. Huge portions of green- 

 stone columns, which have descended from the head of the mountain, 

 are seen reposing in actual contact with the Endogenophyllites-shale 

 (Endogenophyllites being the name given by Professor M'Coy to a 

 new plant-impression which I discovered in that formation). The 

 " Ploughed Pields," as they are locally called, of this mountain, to 

 which I referred in my " Sketch of the Principal Features of the 

 Geology of Hobart Town," read before the Society a few years ago f, 

 are also to be traced to the same cause. 



Before I started upon my examination of the site of the slip, I 

 made particular inquiry among the residents of the district respect- 

 ing the sounds they heard when the event took place. One and all 

 informed me that at first they thought an earthquake had happened 

 — that at five miles distance a rumbling roar was heard at intervals, 

 and it was not till some time had elapsed from the first sound 

 that the destructive body of water made its appearance at the 

 township. This statement fully coincides with the evidences of a 

 series of embankments having been formed, as before mentioned. 



Owing to the subject of this paper being one of no small im- 

 portance at the stage of geological inquiry in this part of the globe, 

 as showing the powerful effects of rainfall as a modifying geological 

 agent, I have been induced to extend my remarks beyond what may 

 be regarded as ordinary limits. Much I have left unsaid relating to 

 more minute details, but hope to supply them at a future date. 



Discussion. 



Mr. W. T. Blanfokd mentioned somewhat similar landslips as 



* Vide paper read by me before the Boyal Society of Tasmania, on the 12th 

 April, 1864. f Quart. Journ. Geol. Soc. toI. xx. p. 465. 



