OF THE HAW An AN ISLANDS. 445 



This I infer from their presence mostly on the leeward side of the islands which are themselves 

 on the lee of Maui, and also from the entire absence of running water even in small quanti- 

 ties ; the severest rains even hardly form a brook. Molokai has been eroded by both sea and 

 rivers. The eastern end at Halawa is undoubtedly worn by waves when at a lower eleva- 

 tion than at present, and the same agent has removed the windward slopes. On the south 

 side the valleys are not deep, but exceedingly irregular, and often bear marks of the severe 

 freshets that sometimes occur during certain winds. In many cases the streams which have 

 formed the ravines seem ridiculously inadequate to the immense task of excavating the 

 great valleys through which they quietly flow, but these occasional torrents explain the true 

 agency. The craters on the summit of the ridge are the usual sources of the permanent 

 streams which run, almost without cascades, to the sea. This general absence of cascades 

 of any considerable height, — there are several at the eastern end which may compare with 

 some on Hawaii, — characterizes this island. 



Oahu presents many of the features of Molokai (PI. XII), and is eroded by the sea on 

 the windward side, while on the south-west of the Konahuanui range the valleys cut into 

 the heart of the mountain. In speaking of the origin of Oahu, attention has been called 

 to the linear craters and their broken walls. Nuuanu has been cited as an example of a 

 crater completely broken through on both sides. Manoa was also in all probability opened 

 towards the south by the final eruption, and the waters have only had to enlarge the rent 

 thus formed for their passage. 1 The Kaala range is only eroded on the windward side and 

 does not present deep valleys. 



Kauai (PI. XL) is deeply channelled on both windward and leeward sides, and the ravines 

 reach deep into the core of the mountain ; indeed, the Hanapepe and Waimea valleys are 

 deeper and have more precipitous sides than Hanalei, Wainiha, and Lumahai on the north. 

 From the flat and crater-crowded summit the overflow of the marshes which abound there 

 winds down on all sides ; the Hanalei and Hanapepe rivers rising from the same swamp and 

 flowing in exactly opposite directions. 



On all the islands the effect of destroying the timber has been very marked. On Oahu 

 especially the rainfall has been much diminished on the mountains, and the little stream m 

 Nuuanu valley which supplies Honolulu with water is greatly wasted. The introduction of 

 goats and cattle which run loose on the mountains destroying the young and tender shoots 

 of the ohia and koa, the principal trees, and the wasteful and improvident way in which the 

 natives destroy wood, has converted portions of the once moist and wooded mountains into 

 dry pastures where the indigo alone of shrubs flourishes. Should the government take no 

 measures to stop the wanton destruction of the forests, Oahu may become like Niihau or even 

 like Lanai. It would be instructive to present the annual rainfall since the introduction of 

 goats, but no accurate observations have been kept regularly, although the zeal of amateur 

 meteorologists has been awakened from time to time, especially at the Punahou school. In 

 1837 and 1838, Dr. T. C. B. Pvooke kept a careful register of atmospheric changes, from 

 which it will be seen that at Honolulu, the thermometer and barometer were tolerably con- 

 stant through both years while the winds varied considerably and the rainfall was more than 

 doubled in the last year. During the rainy season of 1864-65, the following measurements 

 were taken ; — 



l For an admirable explanation of the formation of valleys petition, Geological Report, p. 290, and Silliman's Journal [n. 

 see Dana's Manual of Geology, p. 635 ; also Exploring Ex- s.], vol. be., pp. 48 and 289. 



MEMOIRS ROST. SOC. NAT. HIST. Vol. I. Pt. 3. 118 



