LANDSLIP IN DANDENONG RANGBB. 33& 



that have quietly slid down en masse without disturbing the 

 vegetation growing on them, and those broken up anyhow : 

 further, we may distinguish between those caused by water 

 and those subsidiary ones due to their lower support having 

 been removed ; a series of these eat back into the hill hke a 

 waterfall scooping out a gully. 



The chief slip took place in Mi*. Robert Singleton's pad- 

 dock, at the back of Mr. Sydney Ellery's residence, which 

 stands on a spur, probably the remnants of a former slip. 

 Several lesser slips took place at frequent intervals during the 

 heavy rains, and still continue when there is much vret 

 weather. On the east, and close to the main shp, are two 

 minor ones ; the foremost has dropped ten feet bodily, and so 

 gently as not to disturb the large trees growing on it ; that at 

 the back, being on steeper ground, is more broken up. 

 In these minor shps, which are mostly confined to the surface 

 soil and a few floating boulders, the trees play a great part. 

 Sometimes by falling they start a slip, but more frequently 

 by binding the earth together they serve to retard the motion 

 of the soil at the back of them. Even in the case of the 

 large slips, trees are to be found growing erect on the edge 

 of a precipice, which leads one to suppose that they have 

 assisted in determining the hue of slip. The slips invariably 

 take a horseshoe form, as the rock breaking away at the 

 weakest point drags away the land at its sides as it sinks 

 down to form a terrace, leaving a natural quarry behind. 

 The country rock is diorite porphyrite, consisting of a 

 greenish grey felspar matrix, thickly studded with crystals of 

 oligoclase, and, occasionally, bebs of quartz, flakes of mag- 

 nesian mica or crystals of hornblende, and containing iron 

 pyrites as an accessory mineral ; in fact, the varieties pass 

 from plagioclase porphyrite into mica and hornblende 

 porphyrite, the whole weathering grey. The soil above this 

 rock is a reddish clay two feet thick. Data to hand is not 

 sufficient to enable us to judge what influence terrestrial 

 movements, in the mountain-building sense, has had in 

 causing these slips, but it is evident that the main cause is 

 due to the jointed nature of the rock, enlarged in many 

 cases by the roots of the vegetation growing on the surface, 

 and wedged open by particles of earth falling in the crevices. 

 Water, with its gases, salts, and acids in solution travelling 

 along these natural water channels have attacked the fel- 

 spathic minerals, forming clay and other secondary minerals : 

 these, while endeavouring to exfoliate, will also exert great 



