COMPARISON OF PUNCHBOWL AND DIAMOND HEAD 481 



the photograph (see plate 61, figure 1), taken from high up Diamond 

 head, showing the eastern rim of the crater. 



Punchbowl and Diamond Head compared 



The structure of Punchbowl is like that of Diamond head. It is 

 mostly composed of tuff, much of which on the side toward the city has 

 its seams filled with calcite. In the quarry below the reservoir both cal- 

 cite and zeolites are found, and an occasional piece of basalt. A photo- 

 graph (see plate 62, figure 2) shows the relations of the tuff to the 

 black ash. The person in the foreground stands upon the decayed upper 

 layer of the tuff. He is looking into the excavated part of the quarry. 

 Behind him are the thick layers of black ash. The hill in the back- 

 ground is Punchbowl. The phenomena prove that the black ash overlies 

 the tuff, and that a long interval must have elapsed between the ejection 

 of the two materials, because the inferior one has been weathered. It is 

 probable that the first material came from beneath the sea, while the 

 later ash, though issuing from the same vent, did not come in contact 

 with water, and with it came another basalt, that on the summit of Punch- 

 bowl and in the dikes radiating from it. The extent of the tuff to the 

 southwest is shown in the well boring at the Queens hospital, where 47 

 feet of it is reported underlying 13 feet of lime sand and 10 of black ash. 

 The Tertiary is well shown in a cutting near by on Vineyard street, 15 

 feet of sand with shells being exposed beneath the black ash. 



Similar relations of the tuff, soil, and ash have been observed near 

 Moanalua, where the tuff has been covered by an ash in which may be 

 seen upright trunks of trees.* On Fords island, in Pearl Eiver lagoon, 

 a thin layer of ash has been found intercalated in limestone.! Eather 

 than assume the ashes to have been erupted simultaneously in the Hono- 

 lulu district, it may be better to say that similar eolian materials have 

 been discharged at intervals through an unknown part of Tertiary time. 



Doctor Dall has noted the greater abundance of limestone in Diamond 

 head, where the tuff is fairly saturated with it, than in Punchbowl. A 

 walk up the southwest slope of Punchbowl will satisfy any one that the 

 seams are as fully filled with this mineral as in the northern part of 

 Diamond head, and in the quarry it is not wanting, accompanied with 

 zeolites. The appearance of this calcareous incrustation is shown in 

 the photograph (plate 63) of veins, filling seams, on the road on the 

 east side of Diamond head. The conchoidal fracture of the larger 

 blocks is coated with calcareous incrustations, and the vertical seams are 



* Geology of Oahu, pi. 6, fig. 2. 

 t Op. cit., p. 52. 



