308 SAMOAN ISLANDS. 
vicinity of the large islands, but they are not of sufficient importance 
to merit enumeration in this place. 
The whole group comprises eight hundred square miles of land, 
nineteen-twentieths of which are contained in Savaii, Upolu, and 
Tutuila. The last three islands in the above enumeration lie near 
one another, and are included within the same horizon. ‘This is also 
true of the first four. ‘Tutuila is more alone, lying about seventy geo- 
graphical miles west of Manua, and forty miles east-southeast of 
Upolu; its principal heights, however, are often seen from the east 
end of the latter island. Rose Island, a small atoll, may properly be 
included with the Samoan Group, as it les in the same range with 
Ofu and Manua, but seventy-five miles to the eastward. The group 
is included between the parallels of 13° 30’ and 14° 30’ S., and the 
meridians 165° and 173° 40’ W. 
All these islands were visited by some of the vessels of the squadron ; 
but my own observations have been confined to Upolu and Tutuila, 
with a hasty glance at Manono, Apolima, and Savaii. 
The islands are similar in geological structure: basalt, basaltic 
lavas, and basaltic and volcanic tufas, are the constituent rocks of each 
of them. ‘They differ, however, in the age of the rocks that cover the 
surface; on some we find the features of the oldest islands of these 
seas, while on others the currents of lava may still be traced, that 
flowed down from some crater or fissure. Profound valleys, mural 
precipices, and craggy peaks characterize the former; and the long 
slopes of a volcanic dome the latter. 
The islands stretch along in a west-northwest direction, and vol- 
canic energy appears to have gradually diminished in the same 
direction; the fires first disappeared to the east-southeast, and were 
last extinguished in Savaii at the opposite end of the line. This is 
the reverse of what took place in the Sandwich Islands, where the 
west-northwest extremity of the group was first extinct. 'Tutuila has 
the aged appearance of Tahiti, and contains no prominent cone or 
crater at centre. Upolu, next to the westward, is characterized in 
part by the deep gorges and rugged peaks of Tutuila, and in other 
portions by the gentle slopes of a recent volcanic region, and the 
scoriaceous lavas of modern eruptions. Savaii, the westernmost, is a 
single volcanic district, resembling Mount Kea; the sloping surface 
of its broadly-spread cone, still remains roughened with numberless 
parasitic craters. 
