48 THE VICTORIAN NATURALIST. 



noticed, but would require either actual examples or models to 

 make it clear. The peculiar sinuosities of the outcropping rock, 

 which are due to this pitch, are clearly seen on the road surface 

 and on the hilltop to the northward. One very fine example nearer 

 to Kew has been ruthlessly hidden by the asphalting of the 

 footpath. 



On a careful examination it was remarked that the crumplings 

 of the rock which were first seen are merely minor ones on a 

 great fold, the axis of which lies near the western end of the 

 cutting. The axis of the fold, which shows of course the lowest 

 or oldest of the series exposed, is occupied by blue rubbly shales, 

 which have weathered somewhat more readily than the thick 

 bedded sandstones immediately overlying them, so that very 

 little rock is seen cropping out near the axis itself, while on 

 either side a wall of sandstone stands up, the sandstone part of 

 the arch of the fold having disappeared. 



In some of the minor crumplings some very interesting points 

 were noticed, which showed in miniature what occurs elsewhere 

 on the large scale. A bed of sandstone is much less com- 

 pressible than a bed of shale, and when a series of such sand- 

 stones and shales are folded by strong lateral pressure there is a 

 tendency for cavities to form along the crest of the arch. Into 

 these regions the shales are forced like rolled out dough, so that 

 in the crest of the arch the bed is perhaps twice as thick as on its 

 flanks. Time would fail us were we to discuss the presence and 

 probable causes of quartz veins such as were seen in the faults 

 and joints, the minerals coating the joints, and the character of 

 the joints themselves, the colour stains due to weathering, and 

 the numerous other points which are so readily illustrated in 

 the field, and which a mere brief description would leave 

 unintelligible. 



Two dykes of some rock allied to basalt were seen, but were 

 decomposed to a greasy clay. Our previous trips, however, 

 enabled the members to recognize the clay as probably derived 

 from such a rock when they were questioned as to its nature. 



Leaving the cutting we climbed to the top of the hill by 

 Bight's Falls, and saw the great plain formed by the lava flow, 

 and standing out from it like islands the series of hills on which 

 Melbourne stands, the Northcote hill, and the great Silurian area 

 to the westward. 



From here we went to the gravel pits near the old toll bar, and 

 a few minutes were spent in discussing the more characteristic 

 features of the deposit. It was pointed out that heavy quartz 

 gravel under the influence of running water would collect at the 

 bottom of a valley, so that what is now a hill top must have in 

 former times been the bed of a stream, or have been near the 

 shore of a sea. The gravel cappings of other hills in and around 



