SOME LOCAL DETAILS. 183 



Iii the Pleistocene period the valley of the Murray bay 

 river has been filled, almost or quite to the level of the 

 highest terrace, with an enormously thick mass of mud 

 and boulders, washed from the land and deposited in the 

 sea-bed during the long period of Pleistocene submergence. 

 Through this mass the deep valley of the river has been 

 cut, and the clay, deprived of support and resting on 

 inclined surfaces, has slipped downward, forming strangely 

 shaped slopes, and outlying masses, that have in some 

 instances been moulded by the receding waves, or by the 

 subsequent action of the weather, into conical mounds, so 

 regular that it is difficult to convince many of the visitors 

 to the bay that they are not artificial. Sir W. E. Logan, 

 in his report on the district, has, in my view, given the 

 true explanation of these mounds, which may be seen in 

 all stages of formation on the neighbouring hill-sides. 

 Their effect to a geological eye is to give to this beautiful 

 valley an unfinished aspect, as if the time elapsed since its 

 elevation had not been sufficient to allow its slopes to 

 attain to their fully rounded contour. This appearance is 

 no doubt due to the enormous thickness of the deposit of 

 Pleistocene mud, to the uneven surfaces of the underlying 

 rock, and possibly also in part to the earthquake shocks 

 which have visited this region. 



At the mouth of the Murray Bay river, the boulder- 

 clay rests directly on the striated rock-surfaces, and 

 is a true till, filled with the Laurentian stones and 

 boulders of the inland hills, though resting on Cambro- 

 Silurian limestone. It is evidently marine, since it 

 contains shells of Leda glacialis ; and many of the stones 

 are coated with Bryozoa and Spirorbis. It is also observ- 

 able that on the N.E. sides of the limestone ridges the 

 boulders are more numerous and larger. Above the 



