W. T. BRIGHAM ON THE VOLCANIC PHENOMENA 



the eruption the ashes are blown to leeward. The windward side would, therefore, be the 

 weakest, and is most easily breached. Lava streams are common about Koko, although it 

 is often difficult to trace them to their source, and both the graystone and red vesicular 

 varieties are found, the former often imbedded in large fragments in the tufa, the edges 

 being as sharp and uneven as if recently fractured. 



The most remarkable object on approaching Oahu, is the high cone of Le&hi or 

 Diamond Hill. It is situated on the shore nearly between Koko and Honolulu, 

 and about eight miles west of the former. Its height at present is from four to seven hundred 

 feet, 1 and its longest diameter at the top, about half a mile. The crater is deep, reaching 

 nearly to the sea level, and contains no lava rock. At the bottom, during a third of the 

 year, a pool of water collects which covers nearly half of the tolerably level bottom ; on 

 the remainder, which is deeply furrowed by rains, wild cotton, a few sidas and argemones 

 flourish, and enough grass to tempt horses to make the difficult ascent and descent. 



Fig. 16. View of Leahi from Punahoii ( s-East). 



This cone is rapidly diminishing. In the winter of 1864, during a severe rain, when 

 thirty-six inches of water fell in a week, a deposit of mud two feet in depth was formed 

 over the inner basin, and the degradation of the exterior was still more extensive. The 

 south-west end, which is the highest point, was formerly quite accessible, but now can only 

 be scaled with ladders or ropes. Most of the exterior has been washed down upon the 

 elevated coral bed which surrounds the cone, forming a deep layer of soil, frequently cut 

 through by rain-channels. The strata exposed by the removal of the exterior, have a dip 

 towards the centre, showing that the whole outside has been removed towards the south and 

 west. The rim of the crater is narrow, and where the exterior slope remains, exhibits an 

 anticlinal axis, the dip being about 35°. 



The tufa of which the hill is composed, 

 is light brownish, inclining in some places 

 to red, and is very friable, breaking easily 

 in the fingers. It consists of thin lamina} 

 usually separated by a calcareous deposit. 

 Coral of recent species occurs imbedded 

 in considerable quantity, often undecom- 

 posed, and in masses of two to twenty 

 cubic inches. The whole region about Leahi is an elevated reef. 



No lavas have issued from this cone, but two large streams surround it, and have poured 

 into the sea at its base over a deposit of sand. The sand has been washed away leaving 

 the lava in broken slabs. In one place this lava, in passing over a stratum of tufa, has 



1 Since the above was in print (1867), President Alexander, of Oahu College, has found the highest point to be 760 feet. 



Fig. 17. View of Leahi from K6ko (N.N.E. 



