36 PROCEEDINGS OF THE GEOLOGICAL SOCLETT. [Nov. 20, 



smoothness being due to the grinding process carried on by the 

 transport of immense masses of rock from the head of the mountain 

 during periodical floods. 



The sight that bursts upon the beholder from this point is ter- 

 ribly wild indeed. Stretching above him to a height of more than 

 1000 feet is an enormous tract having a mean inclination of 32°, 

 and strewed with prostrate battered trees of gigantic dimensions, 

 and ponderous blocks of greenstone, many tons in weight, half- 

 buried in yellow clay and sludge. A clean sweep has been made in 

 the centre of the denuded tract, baring the underlying greenstone 

 and forming a new channel many feet in depth. 



It was with very great difficulty that I reached the top of the 

 slip by skirting its margin, which is densely timbered with huge 

 gum-trees and thick underwood. The face of this steep is thickly 

 covered with great masses of fallen greenstone, while its mean 

 angle, as furnished by the clinometer, is 42°. This fallen rock is 

 evidently the result of a former landslip, since clothed by the tim- 

 ber it now bears. The character of this escarpment, as indeed 

 the whole of the ground surrounding the landslip, furnishes an 

 excellent idea of the quantity of rock, timber, and soil which was 

 precipitated into the gully beneath. Upon examining the head 

 where the mass broke away, I found the greenstone to be highly 

 laminated, and presenting a slope of 43°. Above this, there is a 

 bank of drift from the higher ground 20 feet in depth and consist- 

 ing of smaller fragments of greenstone and gravel imbedded in a 

 matrix of yellow clay. 



As this cataclysm occurred between 10 and 11 o'clock at night, 

 no eye beheld what part of the mountain-side first gave way ; but, 

 taking into consideration the incoherent nature of the soil and sur- 

 face of the bottom rock at this part, and also the very great incline, 

 I am disposed to think that the dislocation happened at this point, 

 through supersaturation and undermining by the great water-flow 

 from the head of the mountain. 



Upon extending my examination to the surrounding localities, I 

 found that not an acre exists, having a mean inclination of 30°, but 

 what bore the most convincing evidences of having been the scene of 

 landslips in by-gone times. As a rule in this island, wherever trap- 

 rocks obtain in the mountain having an inclination of between 25° 

 and 30°, fallen masses of such rocks are usually met with at an average 

 height of from 2000 to 3000 feet above the sea-level, thus affording, 

 as I take it, countless examples of these landslips. Nor can this be 

 regarded as a matter for marvel when the precipitous character of 

 the mountain-system of Tasmania, wherever the trappean series of 

 rocks abound, is taken into consideration. 



The altitude of the head of this landslip T estimate to be about 

 3000 feet above the sea-level. I was, however, unable to deter- 

 mine it with precision, owing to my mountain-barometer having 

 met with an accident. In arriving at this conclusion I am guided 

 by a knowledge of the altitude of adjacent heights. 



In looking at the watershed which collected the aqueous force 



