1872.] WINTLE — LANDSLIP IN TASMANIA. 35 



of close-grained dioritic greenstone, sharp at their edges as gun- 

 flints, and all presenting fresh fractures. These fragments were the 

 result of large masses of that rock (which composes the mountain- 

 summit) having been hurled with terrific violence against each other 

 by the fury of the torrent. It would be no exaggeration to say that 

 some of the blocks of greenstone which have been transported from 

 the mountain-side to a distance of three or four miles weigh many 

 tons. 



Having proceeded about two miles along the course of the rivulet, 

 over limestone, greenstone then makes its appearance, rising into 

 lofty hills on both sides of the watercourse, and covering up the 

 limestone and its associated strata for fully one mile and a half. 

 To the eruption and overflow of this igneous rock is to be ascribed 

 the before-mentioned tortuous character of the rivulet's course, 

 to which, as I shall eventually endeavour to show, must be traced 

 the ruin and desolation that followed. 



Close to the base of the great landslip, the limestone is again ex- 

 posed in the bed of the rivulet, where superincumbent deposits have 

 been recently removed by the flood. The beds have a dip of 10°, 

 "W.S.W., towards the mountain, and a strike nearly due north. A 

 very excellent section of them is here exposed in stair-like ledges, 

 the upper surface displaying much metamorphism by contact with 

 the greenstone. The following Table gives their descending order 

 and respective thickness : — 



Thick- 

 ness, 

 feet. 



1. Brown, thick-bedded sandstone. Upper surface altered for more 



than 1 foot in depth into a semivitreous mass, and presenting 

 more or less rhomboidal joints 20 



2. Arenaceous conglomerate, containing worn fragments of decom- 



posed granite, clay-slate, quartz rock, and mica-schist. Upper 

 surface also metamorphosed 10 



3. Dark blue mudstone, studded with angular fragments of quartz, 



altered, and presenting joints 8 



4. Coarse sandstone, containing rounded fragments of a quartzose 



rock, altered near surface into a compact crystalline mass with 

 rhomboidal joints 11 



5. Blue carboniferous fossiliferous limestone, replete with Spirifera, 



Producti, Terebratulidse, and Fenestella, altered near surface ; 

 rhomboidal j oints 12 



6. Blue mudstone conglomerate, with casts of the foregoing shells and 



corals. Altered near surface 100 



7. Greenstone, fine, close-grained, and compact, lying conformable to 



the above strata. 



The inference to be drawn from the foregoing facts is, that the 

 different strata here treated of presented, at the time when the green- 

 stone composing Mount Wellington was ejected, the same broken 

 and stair-like surface that they do now, and the overflow filling up 

 the inequalities of the older sedimentary rocks produced their meta- 

 morphosed character at the point of contact. 



At the distance of about two thirds of a mile from this natural 

 section the foot of the great slip is gained, the intervening space 

 being occupied by polished greenstone having an angle of 10°, the 



d2 



