UPOLU. 329 
Such eruptions would account for the minute and well-defined stra- 
tification of the tufa, and not less satisfactorily for the perfect preser- 
vation of the coral limestone. The close resemblance to the tufa 
craters of Oahu, and the “sand-hills” of Nanawale, Hawaii, will be 
seen by comparing the descriptions. 
Although these are not lava cones, there is still evidence that lava 
rose in one of the craters during its formation. On the east side of 
Nuutele, for a few yards above the sea, there are two narrow dikes of 
black lava. The tufa near the dike is burnt to an ochre-yellow 
colour, and immediately adjoining it, to a light brick-red. Near the 
dikes there is also a fissure which extends to the summit, where a 
small notch marks its termination. 
Tapanga Point, on the neighbouring shores of Upolu, consists of 
layers of tufa stratified like the islands just described. 
The dip and the mineral character of the tufa are the same. The 
low ridge which forms the point is about fifty feet high. The layers 
of the tufa at the extremity incline thirty degrees to the northeast, 
while a short distance back on the north side they incline to the north 
and northwest; and on the low shores at the southern foot of the 
ridge, from which there has evidently been an extensive degradation 
and removal of the layers, the dip is towards the south and southwest. 
These varying inclinations might be explained on the hypothesis of a 
tufa cone, now to a great extent washed away. Moreover, we detect 
a farther resemblance to the islands in the imbedded fragments of 
coral limestone. These fragments are, however, much more abun- 
dant, and among them we find portions of shells and some large 
masses of coral, occasionally three or four inches thick; and with 
these, the solid basalt also occurs in boulders one to two feet in 
diameter. 
As we go south on the coast, the coral rock becomes more and more 
largely disseminated through the tufa; and fifty yards distant half 
the rock consists of coral sand, with fragments of coral and shells, 
among which I collected some of the common Astreas of the coast, 
and pieces of the large Tridacna. Farther from the point, the layers 
gradually pass into a true coral limestone only a little discoloured 
with volcanic materials, which resembles the shore-layers of coral 
limestone found on many other parts of the island,—a formation still 
in progress at the same level, and with the same dip and other cha- 
racters; and along the same coast, this rock passes into a coarse 
boulder conglomerate, consisting of the loose basaltic pebbles and 
&3 
