76 Cruise of the ''Alert:' 



plentifully strewn with similar fragments of wood, the remains 

 of bygone forests which had perished prematurely. These cir- 

 cumstances are fully explained by the occurrence of soil motion, 

 for as the soilcap by its sliding motion, imparted by gravi- 

 tation, and aided by expansion and contraction of the spongy 

 mass, reaches the water's edge, the soluble portions are re- 

 moved, while its more durable contents are left to accumulate 

 at the foot of the incline. In this way rocks and stones may 

 sometimes be seen balanced in odd situations near the sea 

 beach, simulating the " roches perchees " which are dropped by 

 a melting iceberg or a receding glacier. These circumstances 

 are all the more interesting from their occurring in a region 

 where the effects of old and recent glacial action are exhibited 

 to a marked degree. Planings, scorings, striations, and " roches 

 moutonnees " may, one or other, be almost invariably found 

 wherever the rock is sufficiently impervious to the disintegrating 

 action of the weather to retain these impressions. Thus they 

 are nowhere to be seen on the coarse-grained friable syenite, 

 which is the common rock of the district ; but where this rock 

 is intersected by dikes of the more durable greenstone, the 

 above-mentioned signs of former glacial action may be seen 

 well developed. I speak now of old glacial action, because 

 we have not found any glacier existing in the neighbourhood 

 of the Trinidad Channel, from whence they seem to have 

 entirely receded ; but they are yet to be seen in the fiords 

 of the mainland further north ; and in the main Straits of 

 Magellan we had opportunities of studying fine examples of 

 complete and incomplete glaciers, exhibiting in all its grandeur 

 that wonderful denuding power which these ponderous masses 

 of ice exercise as they move silently over their rocky beds. 

 There are, therefore, in this region, ample opportunities of 

 comparing and differentiating phenomena, which have resulted 

 from former glacial action, and those which are due to soil- 

 motion — a force now in operation. 



