676 REVIEWS AND BOOK NOTICES. 
the hills. ‘‘ But the areas of subsidence, which covers an extent 
of fifty thousand square miles in the Pacific, and which commands 
so much interest from its bearings on geological questions, are 
indicated by” (1) ‘the existence of wide and deep channels be- 
tween an island and any of its coral reefs; or in other words, the 
existence of barrier reefs; (2) the existence of lagoon islands or 
atolls; (3) the existence of submerged atolls; (4) deep bay 
indentations in the coasts of high islands as the terminations of 
valleys.” 
‘Each atoll” says the author, * could we measure the thickness 
of the coral constituting it, would inform us nearly how much 
subsidence took place where it stands; for they are actually so 
many registers placed over the ocean, marking out, not only the 
sight [site] of a buried island, but also the depth at which it lies 
covered.” As to the extent of the subsidence we are told— 
‘It is very evident that the sinking of the Society, Samoan 
and Hawaiian Islands has been small, compared with that required 
to submerge all the lands on which the Paumotus and the other 
Pacific atolls rest. One, two or five hundred feet, could not have 
buried the many peaks of these islands. Even the one thousand 
two hundred feet of depression at the Gambier Group is shown to 
be at a distance from the axis of the subsiding area. The groups 
of high islands above mentioned contain summits from four 
to fourteen thousand feet above the sea; and can we believe it 
possible that throughout this large area, when t í 
islands now sunken were above the waves, there were none 0 
them equal in altitude to the mean of these heights, or nine 
e thousand 
thousand feet? That none should have exceeded nin : 
within probable bounds, we shall not arrive at a more 
change of level than our continents show that they ae 
gone; for since the Tertiary began (or the preceding perio“ ded 
Cretaceous, closed) more than ten thousand feet have uae" ue 
to the Rocky Mountains, and parts of the Andes, Alps an a 
alayas. 
Between the New Hebrides and. Australia, 
the reefs and 
h may have et 
an 
simultaneously in progress. The long reef of one a ‘a wide 
ty miles from the north cape of New Caledonia, an 
st 
barrier of Australia is proof of great subsidence, 
border of that continent. But the greatest amoun 0 
