During Post-Miocene Times. 5 



motive power to be available, still the boulders would be 

 reduced "to pebbles while they were in the act of being con- 

 veyed between the ranges and the Murray. And yet great 

 boulders, which must have travelled long distances, abound 

 in the Murray bed, at the Campaspe junction, and else- 

 where (Hodgkinson " On the Geology of the Inter-Mitta- 

 Mitta and Campaspe," R S. T., Vol. I.). 



Surely their wide distribution requires some other agency 

 than that of flowing water. If, knowing as we do that the 

 sea covered these plains not long since, we seek it in the 

 ocean, we still fail to find any evidence that its waters could 

 have formed these deposits. The transport power of the 

 ocean is very limited. Where very strong currents prevail 

 strips of boulders occasionally line the strand, but they 

 never move seawards, and only during storms do they travel 

 along the coast at all. If a sea margin is encroaching on the 

 land these deposits are in time left out at sea, and in this 

 manner they may acquire a travelled appearance. But they 

 lose their size, as they pass through the surf, by getting 

 ground down. When Darwin found Patagonia buried under 

 a superficial stratum of such materials, he at first imagined 

 that the boulders might be products of the ocean, and he 

 tested the neighbouring seas to ascertain if they were simi- 

 larly boulder-strewn. Careful soundings showed him that 

 the boulders were always ground into pebbles before they 

 left the surf. At a distance from the shore of three miles 

 they were never larger than a walnut ; at seven miles there 

 were none larger than a filbert, and at twenty-two miles out 

 they had been reduced to a coarse sand, the grains of which 

 were not larger than one-tenth of an inch in diameter. And 

 he found that throughout this width of littoral the diminu- 

 tion in size of the stones was gradual (Geological Notes on 

 South America, p. 16). We may therefore dismiss the 

 ocean from our minds, as far as this deposit is concerned. 



Upon a review of all the circumstances, it appears to me 

 that the sculpture and distribution of boulders is not, in the 

 main, due to water-power, and I am acquainted with only one 

 agency which is capable of doing the work, and that is ice. 



The power of ice is unquestionable. Frost breaks up 

 rock surfaces rapidly, and wedges off masses. The surface 

 ice of frozen streams destroys the river sides. Ground ice, 

 or anchor ice, as it is sometimes called, envelopes the 

 boulders and gravel of the stream bed, lifting them up, and 

 floating them along with the current. In this manner 



