Vol. 8, 1922 
GEOLOGY: W. M. DA VIS 
11 
As to the first line of evidence based on the absence of cHffs on Tagula: 
If abrasion by the lowered ocean had operated long enough to cut a plat- 
form 10 or 20 miles wide beneath the present floor of the southern com- 
partment, it ought at the same time to have cut spur-end cliffs on the north 
shore of the main island, where the defending reef is a fringe only half a 
mile wide; and these cliffs ought still to show the upper part of their faces 
as plunging cliffs, now that the ocean has resumed its normal level; but 
the charts show no such cliffs. 
The second line of evidence based on the absence of cliffs on the Calvados 
islands is similarly argued. It may be added that the absence of cliffs 
at these significant points on the charts of the Louisiade islands does not 
appear to be due to poor charting; for on the coast of Misima, where 
Maitland observed the white limestone scarps of elevated reefs, the charts 
clearly show a shore cliff, and a legend is printed along it: "Cliffs 100 
feet high." 
As to the third line of evidence: The little outpost islands are so nu- 
merous in the Tagula barrier-reef loops around the northern lagoon com- 
partment and around the western part of the southern compartment 
that it seems unreasonable to believe the waves of the lowered Glacial 
ocean could have cut their way behind the outposts efficiently enough to 
abrade a platform 10 miles in width. Not only so, the outpost islands 
show no sign of being clift on their outer sides. One of them, Utian, a 
miles across and 480 feet high, is reported by Maitland to consist of vol- 
canic rocks; but it is not a young volcanic cone built up in Postglacial 
time, for the chart shows it to have well dissected form, with three slen- 
der points enclosing two small bays turned toward the outer ocean; yet 
the points are not cut back in plunging cliffs. Another outpost not 
far away is said by the same observer to consist of limestone; this island 
cannot have been made and elevated since an assumed platform was 
abraded, for the height of the island, 530 feet, is so great that, in such 
case, the platform thereabouts ought to be more or less emerged; and 
it cannot have been made and raised before the platform was cut, for in 
such case the limestone ought to have been consumed by the waves that 
cut the platform. 
The small outpost islands of the Tagula barrier reef therefore give 
strong confirmation of the evidence against abrasion derived from the 
absence of plunging cliffs on the north side of the main islands and on 
the terminal members of the Calvados chain. But if the northern com- 
partment of the Tagula lagoon, which is alone as large as many an atoll, 
is thus shown not to be underlaid by an abraded platform, there is no 
sufficient reason for thinking that the southern compartment or indeed any 
other barrier reef or atoll lagoon in the whole Pacific has any such 
smoothly prepared foundation. Surely, if the flatness of the floor and its 
