50 
The N.Z. Journal of Science and Technology. [April 
(its greatest breadth being twenty-seven miles); the Apolima Strait occu¬ 
pies nine miles ; Upolu has a length also of forty-seven miles (its greatest 
breadth being only sixteen miles); the distance to Tutuila is forty-four 
miles ; and the length of Tutuila in an west-east direction is twenty miles 
(its breadth being only six miles). The Manua group lies sixty miles a little 
to the north of east of Tutuila, and is also elongated in a west-north-west 
to east-south-east direction, with a total length from Ofu to Tau of fifteen 
miles. The form of the sea-bottom between Upolu and Tutuila cannot be 
gleaned from the Admiralty chart, nor that between Tutuila and the Manua 
group, but it seems from the directions of elongation that there are probably 
two elevated ridges rising from the sea-bottom en echelon , the one bearing 
Savaii, Apolima, Manono, Upolu, and Tutuila, and the other the islands of 
the Manua group, rather than a continuous ridge connecting the latter to 
the former. All the islands are mountainous, rising to heights of 6,096 ft. 
(1,858 m.) in Savaii, 3,607 ft. (1,099 m.) in Upolu, 2,133 ft. (653 m.) in 
Tutuila, and 2,500 ft. (762 m.) in Tau. 
The Samoan Islands lie north of the northern end of a tectonic line 
running north-north-east from New Zealand through the Kermadec and 
Tonga Groups. To the east of the middle part of this line lies the great 
Kermadec-Tonga deep. To the west is the intermittent sub-oceanic plateau 
bearing the Kermadec and Tonga Islands, generally interpreted as a con¬ 
tinuation of the mountain axis of the North Island of New Zealand. West 
of this is a depressed belt with a line of active or dormant volcanoes— 
Ruapehu, Ngauruhoe, Tongariro, Tarawera, and White Island in New 
Zealand, Curtis and Sunday Islands in the Kermadec Group, and Falcon 
Island, Tofua, Metis, Late, Fanua-lai, and Wesley Rock in the Tonga Group, 
besides other submarine centres of eruption. Speight has suggested that the 
fissure on which these volcanoes lie is extended to the north-east to intersect 
Savaii and the Hawaiian Islands. The Tongan plateau, however, curves 
round to the north-west before reaching Samoa, and extends in this direction 
as far as Alofa and Fotuna, and the active volcano of Niuafou seems to show 
a similar bend in the volcanic line. The Samoan line of volcanoes has a trend 
more or less parallel to this north-west trend of the Tongan plateau, but is 
separated from it by deep seas, and it is very improbable that Speight’s 
suggestion has any force. 
Of the Samoan Group, Tutuila, the Manua group, and Rose Island 
belong to the United States, and are administered through the Navy; while 
Savaii, Apolima, Manono, and Upolu form Western Samoa, which is now 
held by New Zealand under mandate from the League of Nations. 
The best maps of Western Samoa are the German Reichs-Marine-Amt 
charts of Savaii, 1912, and of Upolu, 1914, both on the scale of 1:150,000. 
The British Admiralty chart, No. 1730, of the Samoa or Navigator Islands, 
is based on German and American charts to 1912, and gives a useful general 
view of the group. No geodetic survey or triangulation has been attempted 
either in Upolu or Savaii, and the positions of the mountains and the courses 
of the streams are very imperfectly shown on existing maps. 
With the exception of the coral reefs along the coast and some beach 
deposits to be noticed later, all the rocks of the islands are of volcanic origin, 
and, so far as hand-specimens go, are mainly of basaltic facies. In this respect 
there is a distinct parallel with the Hawaiian Islands. A further parallel 
exists in regard to the shifting of the centres of volcanic activity. Savaii 
has experienced three eruptions in historic times, and is comparable in 
form and state of erosion with the Island of Hawaii. Upolu bears at its 
