2 The American Geologist. January, looi. 
must have been intermittent with long quiescent periods to 
enable the shore to have become repopulated with mollusks 
and corals." A good picture of Diamond Head appears op- 
posite page 40 preceding. 
It is necessary here to remark upon two serious errors of 
observation committed by Dr. Dall. It is true that Diamond 
Head was deposited in shallow water, its center being about 
one mile outside of the previously existing shore line. I un- 
dertake, however, to question the idea that it has since been 
"gradually elevated." Such elevation if it occurred must 
have been some 200 feet to have exposed what he calls a ma- 
rine formation on its seaward base. Dr. Dall should have ob- 
served the total absence of marine erosion around the sides of 
tlT£ cone, upon the soft material of which the action of the 
waves would have been extremely destructive There is also 
no trace of such erosion around the evidently older tuft-cone of 
Punchbowl, four miles away, nor any elevated beach marks 
along the neighboring mountains. 
Dr. Dall's second error of observation was in attributing a 
marine origin to the mass of material lying against the sea- 
ward base of the crater. That mass is composed of mingled 
small angular fragments of tuft fallen from the hights above, 
with large quantities of calcareous beach sand. Pervading the 
mass are numberless laminated calcareous concretions, which 
Dr. Dall has mistaken for coral reef. These fragile laminated 
crusts are identical with those forming the interior structure of 
our numerous calcareous sand dunes. The layers constantly 
vary in angles of dip, corresponding to the formerly varying 
surfaces of the dunes. Had the tuff enclosed ever been ex- 
posed to the action of the waves, so far from retaining its 
angular fomis, it would immediately have been ground into 
soft mud. 
The whole mass is of Aeolian formation. It is simply a 
great sand-dune. The contents have been assorted by the 
wind, the eastern end being composed mainly of larger frag- 
ments of tuff, and the western end, one-third mile away, main- 
ly of sand much triturated, and stained by the brown tuft'. 
The mollusks of Tertiary age enclosed in the mass, as found 
by Dr. Dall, may be fully accounted for as having fallen from 
the hisrhts with the tuff. Thev were torn off from the ancient 
