Brevity of Tuff-Cone Eruptions. — Bishop. 3 
submerged reefs and beaches traversed by the shaft of the 
eruption. I have found large shells embedded in the laminat- 
ed tuff at Koko Head, as well as corals. Farther evidence is 
found in the fact that fragile land mollusks are enclosed be- 
tween the crusts in great numbers side by side with the marine 
shells. Both fell together from the cliffs above. 
My main contention, however, is to prove the absolute im- 
possibility that a crater like Diamond Head should be a 
product of "intermittent ejection" with "quiescent periods," 
even brief ones, or that it could have been "slowly deposited." 
I propose to prove that a cone of such peculiar form and 
structure could have been created only by an extremely rapid 
projection aloft of its material, completed in a few hours at 
most, and ceasing suddenly and finally. 
My first proof of this conclusion is derived from the ex- 
treme regularity of the elevated circular rim of this cone, such 
as could be the result only of a single, rapid, uniform, uninter- 
mitted outthrow of the tuft'. Two-thirds of the elevated peri- 
meter is part of an almost perfect circle of about 5,000 feet 
in diameter, and of a comparatively uniform hight, about 450 
feet above sea-level. The tuft" is piled up in this regular ridge, 
originally rounded on its top, in very uniform quaquaversal 
layers or lamniae, whose steepest dip on the outside is about 
35°, and much less on the inside of the broad bowl. The 
great subaerial erosion discloses the interior structure of the 
rim, although it has not obliterated the really delicate sym- 
metry of the original form. (See Plate 8, Vol. 11, p. 46.) 
The southwest third of the perimeter of the crater is mas- 
sive, attaining a present hight of 762 feet. It is severelv 
wasted by the impact of storms, and was once probably 1,000 
feet high. The original rounded summit must have been 
considerably to seaward of the present sharp peak. The orig- 
inal form may be best understood by comparison with those 
of Koko Head and of Lehua island, which are of somewhat 
similar form and dimensions, but remain substantially unal- 
tered in their rounded summits. The immense enlargement 
of the southwest portions of these craters, as well as of many 
others is doubtless correctly attributed by W. L. Green to the 
action of the strong trade winds deflecting to leeward the lofty 
jet of tuff, and piling it up disproportionately on that side. 
