233 [Mann. 



Denudation takes place here very rapidly ; the lavas bcino; of a soft 

 basaltic structure, often with layers of scoria interstratified with more 

 compact masses, some of which exhibit the columnar structure of ba- 

 salt very finely. A stream of water once getting a passage into these 

 softer scoriaceous beds will fast undermine whatever more solid ma- 

 terial there is above. Professor Dana, in the Geol. U. S. Expl. 

 Exped., has well shown the different ages, in relation to one another, 

 of the different mountains of the group, and this can not fail to 

 attract any one's notice in the different degrees of denudation, i. e., in 

 the difference of the sizes of the valleys formed in different mountains. 

 In the western end or mountain of the island of Maui, this denudation is 

 strikingly exhibited. We have here a conical mountain of nearly 

 six thousand five hundred feet, thus rising to a height of about one 

 thousand feet above the general level of the clouds, — remaining 

 but a mere framework of what it originally was. Radiating in 

 different directions towards the coast, are seven very large valleys, 

 besides others smaller, which one may throw a stone into, severally, 

 by walking less than a quarter of a mile. The valley of Wailuku, 

 opening on the northeast side of the mountain, is three or four miles 

 in diameter, both longitudinally and transversely, with a depth of six 

 thousand feet, bounded on either side by nearly vertical walls which 

 merely serve to shut it off from two other valleys of but little less 

 size ; one of which opens seven miles north and the other four miles 

 south, while in places the separating walls are so thin that one can 

 sit astride of them, one foot in one valley, and the other in another. 

 A third valley opening twenty or more miles farther to the south 

 actually cuts into Wailuku valley to so great an extent that in olden 

 times the natives preferred to cross by the pass one or two thousand 

 feet high rather than go around by the coast. The valley of Hona- 

 kahau which opens on the opposite or west side of the island, cuts into 

 the head of Wailuku valley also. 



This is what we see on a conical peak. On the island of Oahu, 

 which has a northern range of mountains, instead of a single peak, 

 condensing the moisture of the clouds along its whole length, we 

 have parallel valleys to the number of thirty or forty, on the south- 

 ern slope. The northern side of the range, for thirty miles, is 

 one stupendous cliff, from two to four thousand feet in almost per- 

 pendicular height. But again, at the western end of this range, 

 where the mountains slope in three directions from the centre, the 

 fourth being a cliff, we see, in a less marked manner, the features of 

 West Maui. The southern range of Oahu also shows the same marks 

 of denudation, the latter being governed by its shape, which com- 

 bines a peak with a range on either hand. 



On the island of Kauai, there are many grand featm-es of scenery 



