266 THE INFLUENCE OF INANIMATE SUKEOUNDINGS. 



Pacific Ocean. This current, in conjunction with those caused 

 by the ebb and flow of the tide, impinges perpendicularly on the 

 broad side of the group ; hence on their eastern side there is a 

 triangle of comparatively still water, since the main current 

 must part before the insuperable barrier ; and, within it, only 

 the more superficial currents can produce any efiect. These, 

 however, here in the Pelew Islands flow almost constantly from 

 east to west ; on the eastern reef a long line of breakers is always 

 visible even during the short period of the south-west monsoon, 

 and even at the highest tides it is always dangerous to cross the 

 reef here. On the western reef, on the conti'ary, at high tide 

 and in a calm sea, the water over the exterior edge of the reef 

 is so perfectly still that it may be paddled across in a boat with- 

 out any danger. The currents which run past the islands to 

 the north and south, or between the separate islands, whether 

 as tidal currents or as part of the great north equatorial current, 

 on the west side, turn at an angle to the north or south. In 

 correspondence with these facts we see that in a rough sea a 

 wave falling on the outer reef propagates itself in the direction 

 indicated, while analogous waves on the east break simultane- 

 ously on almost the whole length of the shore. In connection 

 with this, indeed, there is another fact which surprised me very 

 much the first time I observed it. It is usually supposed that 

 while the tide is rising, the water that flows in the lagoons or 

 lagoon channels is thrown into them over the outer margin of 

 the reef. This is certainly not the case in the Pelews ; almost 

 all the water flows into the natural channels as readily as it 

 flows out of them. This is proved by the fact that during the 

 rising tide the current produced on the surface of the reef 

 does not flow into the channel from the outer reef, as would be 

 expected if that hypothesis were correct, but on the contrary 

 from the channel towards the reef. During my first expedition 

 on the western reef, my life was in some danger from this cir- 

 cvimstance, then unknown to me, for I had gone so far from the 

 boat that I had great difiiculty in gettuig back to it again. 



Let us now endeavour to explain the observations I have 

 communicated on the assumption that both these classes of 

 currents were active agents during a period of upheaval in 



