GOLD REGIONS OF STRAIT OF MAGELLAN 695 



it may be said that the alluvial deposits in the creeks and on the 

 hillsides have doubtless been derived from the erosion of gold-bearing 

 rocks, and though such rocks have not yet been found to any great 

 extent in the region, they nevertheless probably exist and may some- 

 time be discovered. If the Magellan region represents the partly 

 submerged southern end of the continent, as already mentioned in 

 this paper, many of these deposits may have been originally formed 

 as ordinary alluvial deposits high up in the mountains, and brought 

 down during the sinking era to a much lower level, while some of 

 them may have been completely submerged in the sea. The gold 

 in the beaches probably came largely from the later erosion of the 

 alluvium in the creek beds and on the hillsides, and perhaps partly 

 from old submerged alluvium from which the gold was thrown up by 

 the sea. In either case the gold has been further concentrated by 

 being washed over and over again on the beaches. It is said that the 

 beaches, after having been carefully worked for gold, seem again to 

 become rich in that metal after a storm or an unusually high tide.^ 

 This phenomenon is probably due partly to the action of the waves 

 and currents in concentrating the gold which the imperfect methods 

 of the miners have left behind in the sand, and partly to the washing 

 up of fresh gold-bearing sand from depths that are undisturbed in 

 ordinary weather or by ordinary tides. So well recognized is this 

 enriching of the beaches, that the miners, after working all the sand 

 that can be profitably handled, wait for the next storm or very high 

 tide to come, and then wash the same spots over again with a good 

 profit. 



The ordinary tides in the eastern part of the Strait of Magellan 

 have a rise and fall of 30 feet or more, and the spring tide, 45 or 50 

 feet, though in the western part of the strait the tides have a much 

 less rise and fall. The great rise and fall of the tides on the Atlantic 

 side cause rapid currents in the strait, often with a velocity of 7 or 8 

 knots an hour, and these, scouring the beaches backward and for- 

 ward, must have a very marked effect in concentrating the gold. 

 When we consider that a river, flowing always in one direction, has a 

 wonderful power to concentrate gold in the gravel in its bed, a much 



lA similar phenomenon is observable in the gold-bearing beach sands of Cape 

 Nome, Alaska. 



