THE BUILDING OF AX ISLAND. 63 



width, intervenes between the present' sandy shore and a small reef of beach- 

 limestone, which marks a former shore-line. 



Another evidence that the rockv points cannot for ever protect the shores 

 of the bays is found in the low cliffs formed of debris which in many places 

 has been washed from the hills by the rains, cliffs which show by their abrupt- 

 ness that an encroachment is being made upon them, as, for example, at Great 

 Pond, at La Vallee, and at Ham's Bay. 



Thus we perceive that the sea is continually eating away the land at its 

 edges, and only requires time to bring it all down beneath the sea-level. 



Even the reefs, which arc really magnificent protectors, because covered 

 by living coral, which is always able to maintain itself against the waves b)^ new 

 growths, and even in case of the gradual subsidence of the bottom can keep 

 the reef by such growth nearly up to the level of the water, yet these wonder- 

 ful reefs even cannot save the land from ultimate destruction, for the continual 

 currents and the occasional storms can work a way inside them and mav ulti- 

 mately leave them isolated out at sea, as most likely has been the case with the 

 reefs which we find a mile or two out at sea along our southern coast. 



Sandy Points, like the two above-mentioned exceptional cases (Krause 

 Point and Sandy Point), can only exist under special conditions, the trend of 

 the coast and the existence of extensive reefs may direct the currents in such 

 a way that the sand is deposited, instead of being carried off'; but in the long 

 run these special conditions must be changed and the protected sandy points 

 will be removed as surely as are their rocky neighbours. 



It appears, then, that granted time enough, the land could be eaten away 

 by the sea alone, but when we study attentively the agents that are at work on 

 the surface of the land, we shall see that if a considerable part of the wearing 

 away is due to the sea, a far greater part appears to be due to the rains and 

 the streams. 



It is certain that the material which makes our present land has not been 

 put down in the sea in the form of hill and dale as we now see it, but that this 

 form has been given to it since its upheaval. Let us take, for the sake of 

 illustration, the hills at Anna's Hope and at Work and Rest, on opposite sides 

 of the Grange Valley (Figures 24 and 25). When we examine the strata in 

 these hills we do not find them taking the slope of the hillsides ; but we find 

 that they come out of the hillsides as though they wei"e once continuous across 

 the intervening valley, and the more we examine the question the more con- 

 vinced we shall become that such really was the case. 



It seems, then, that the valley has been carved out of the uplifted strata, 

 and the hills are what is left behind. From this point of view it is the valleys, 

 and not the hills, which are the positive features in the landscape, and after we 

 have understood the facts connected with the elevation of our island, it is the 

 valleys which we must study first if we wish to know anything of the sculptur- 

 ing of its surface. 



First, then, let us ask bv what tools the excavation of the particular valley 



