1872.] WLNTLE LANDSLIP IN TASMANIA. 37 



necessary to remove so large an area of the surface of a mountain's 

 side, and then remembering the terrible effects produced in the lower 

 regions, the mind of the geologist is constrained to have recourse to 

 an accumulation of such power and its sudden liberation. In tra- 

 versing the bed of the rivulet it is seen that where the carboniferous 

 limestone obtains in the lower levels, there the huge trees and rock- 

 masses brought down by the torrent began to be deposited. But 

 when the greenstone formation is reached, which, as before men- 

 tioned, rises in lofty hills on either side of the channel, giving to it its 

 labyrinthine course, startling evidence of the force of the obstructed 

 deluge is to be seen. The escarpments of these hills bounding the 

 rivulet are so arranged that, could both sides of the gully be made 

 to meet, they would fit into each other like the serrated edges of a 

 cranial suture. The first thing which strikes the observer at this 

 point is, that the water had swept every thing before it to a height 

 of 60 feet on one side of the gully, and only reached to 12 or 15 feet 

 on the opposite side. This feature is to be seen alternating until 

 the foot of the landslip is reached. This phenomenon is to be 

 accounted for, I believe, in this way. 



When the first mass of earth gave way, at or near the head of the 

 slip, it formed an embankment or dam where the angle of the incline 

 is least ; the accumulated water at last bursting its bounds, the 

 whole mass was precipitated into the gully below, carrying all before 

 it, and, striking the point of the hill at the bottom, a great wave of 

 deflection would be hurled on the opposite side, where an indentation 

 exists ; and much of its force being now expended, another dam was 

 formed by the huge trees and rocks ; and thus a repetition of dis- 

 ruptions of bodies of water occurred. This is to be seen in several 

 parts of the rivulet by the arrangement of the stones. "When the 

 first great body of water had been thrown to a height of 60 vertical 

 feet on one side of the gully, it deposited at its edge the trunks of 

 enormous trees. One of these I found upon measurement to be 

 103 feet long, without the sign of a branch, and 6 feet in diameter at 

 its base. It had been snapped off short at the smaller end, which 

 gave a diameter of 4 feet 2 inches. These trees were lying parallel 

 to the direction of the wave. Close to this spot, on the same escarp- 

 ment, stood trees of equal size without a vestige of bark, that had 

 been broken off 30 feet from their base. A few hundred yards from 

 this spot one large blue gum-tree had fallen right across the gully 

 and snapped in three places. This tree measures in length 213 feet, 

 with a diameter in the middle of 4 feet 9 inches. fl In some instances 

 masses of greenstone had been driven into the solid wood as though 

 propelled from a cannon. 



That this landslip has been the greatest geological mutation in 

 this island within the memory of man there cannot be a doubt ; but 

 it is only one of many thousands that have taken place on a similar 

 scale during the Tertiary epoch. 



For more than a square mile in the flat low-lying area oc- 

 cupied by the township of Glenorchy, water-worn masses of 

 greenstone, limestone, and sandstone are seen to a depth of 



