4 Evidences of a Glacial Epoch in Victoria 



Text Booh, p. 363), and that they are the most powerful 

 fluvial agents known. But they lose their power when they 

 leave the mountain side, so that their agency will not avail 

 us to explain the occurrence of boulder deposits out on the 

 distant plain, or far down gentle valleys. 



Nevertheless, as many of our conglomerates occur 

 amongst the hills, we will see what may be the precise 

 nature of torrential action. 



On the coast of the Mediterranean, between Toulon and 

 Genoa, the Alps rise almost sheer from the beach, and a 

 number of streams descend through steep mountain gorges 

 and plunge into the sea. For eight months in the year their 

 beds are dry, and during four months the snow waters come 

 down in tumultuous torrents, spreading out fanwise directly 

 they reach the mountain foot. No water-power of greater 

 force per volume than these streams show is known ; and 

 yet, with all their force they are unable to keep open their 

 own channels. As the flood widens out on the short, flat 

 coast- strip, it weakens and drops its load. All that enters 

 the ocean is sand and mud, with some lime in solution. A 

 mass of shingle lines the strand. 



Every year, after the snow waters have ceased to flow r 

 the Governments of France and Italy have to. spend much 

 money to clear the coast road of the bouldery rubbish which 

 these torrents leave behind them. The same phenomena are 

 repeated wherever mountain streams reach the level lands 

 below, for the boulders come to rest directly the torrential 

 character is lost (Ly ell's Prin., Yol. L, p. 491). Therefore, 

 if our conglomerates were the product of torrents, they 

 would occur in fan-shaped deposits of limited extent, which 

 is certainly not the case ; for, on the contrary, our boulders 

 straggle all over the country in irregular streaks, sometimes 

 fifty miles long. 



If we can suppose the above objections to the fluvial 

 origin of the boulders to be explained away satisfactorily, 

 there yet remains another difficulty in the way of its 

 acceptance. This lies in the fact that the violent nature 

 of this mode of transport is such that the boulders would 

 be ground down into gravel, sand, and mud long before they 

 could reach the distant points at which we find them. Pro- 

 fessor Geikie states that granite blocks lose 40 per cent, of 

 their bulk by the time they have travelled the first fifteen 

 miles, although the rate of wear is less afterwards (Geikie's 

 Text Book, p. 372). Therefore, if we could suppose the 



