100 MICHIGAN ACADEMY OF SCIENCE. 



The importance to future investigators of such a succinct and com- 

 prehensive statement of conclusions is manifest. 



The actual geological history of the island of Oahu is to be reached 

 by reading backward, as I have already said, the general story I have 

 outlined, starting with the concluding chapter as its record is pre- 

 sented in the existing features of the island. The fringe of coral reef 

 rock just above sea level all around the coast constitutes that last 

 chapter, telling of a recent emergence of the land as a whole from the 

 sea. Restore the old sea level and we shall see the island as it was 

 in the immediately preceding stage, its land area materially less than 

 at present. 



The present surface of the island is encumbered with material dis- 

 charged from recent volcanic vents, all this we must clear away in 

 imagination. The scenery about Honolulu will be robbed thus of its 

 most striking and distinctive features. The Tantalus group of sand 

 hills must go first, laying bare once more sharp ridges corresponding 

 with those on either side. The convenient grading up of Nuuanu valley 

 from the city to the "pali" is an innovation not to be tolerated, we must 

 restore the old valley bed, much more contracted than at present, and 

 growing steeper as it is ascended according to rule. Picturesque Diamond 

 Head may remain for a while, but it must go before long, with Punch- 

 bowl and Koko Head and the rest of the tufa cones of the peripheral 

 region, and so must Rocky Hill and Kaimuki. I am not now indicating 

 the precise order in which they must be banished but insisting simply 

 that they must go from our mental picture. 



Next we must restore flesh to the bones of our skeleton island, adding 

 material at every point where we find erosion particularly active, 

 exactly reversing thus the process by which the land has been shaped. The 

 valleys on the leeward side must thus be filled first, the mountain tops 

 raised until they form a barrier to keep back the rain, and then the 

 work of rapid reconstruction must be transferred to the windward 

 side. We must lift our island as a whole once more out of the water, 

 restoring a condition which shall permit the growth of corals on its 

 fringe where today the ocean stands at a level a thousand feet higher. 



We must picture the Koolau mountain when it was almost a counter- 

 part of what we see today on Molokai, its leeward side almost intact, 

 its windward exposure eaten into by stui)endous ampitheaters of erosion, 

 and then we must call up from the depths of ocean the great slices of 

 the old island that have parted from the mountain mass by faulting. 

 We shall have a vision at last of a volcanic dome not less than 6,000 

 feet high, sloping gradually to the shore line on the south, resting 

 against the Kaala mountain on the west and ending on the northeast 

 in an escarpment of cliff somewhere beyond Mokapu point. 



All this time we shall have seen onlj- a slow progress in the restoration 

 of the Kaala mountain, sheltered as it is from the trade wind bv the 

 Koolau luounfain. But now we have to watch a reversal of the process 

 by which this latter was built up. Once more we see the mountain 

 blazing at intervals with the volcanic fires which have heaped up 

 over its great dome hills of scoria and marked its surface with the 

 blackened and desolated track of lava streams. The great eruptions 

 which occasionally pour into the ocean rivers of molten rock now 



