(6) In only two localities is the temperature at or near the boiling-point. In one place it is 180° F., and in most of the other springs it ranges between 100° and 150°.
(7) Siliceous sinter is formed where the temperature is over 150°.
(8) As exemplified by the water of the Savu-savu springs the proportion of salts in solution (8 per 1000) is constant over many years; whilst in this fact and in the relative amounts of each salt there is a sharp distinction from the composition of sea-water.
(9) The hot springs are older than the streams and rivers, along which they are so frequently found.
It would appear that they are largely supplied from the “soakage” of the heavy rainfall in the mountains.
CHAPTER IV
DESCRIPTION OF THE GEOLOGICAL AND GENERAL PHYSICAL FEATURES OF VANUA LEVU.
In this chapter the detailed description of the island is commenced, beginning with the western extremity and proceeding eastward. Most of the petrological details are dealt with under their respective sections; but it has been found necessary also to frequently refer to them in this connection.
The Naivaka Peninsula.—This mountainous peninsula forms the conspicuous feature of the western extremity of Vanua Levu. Amongst all the mountains of the island its appearance from a distance gave most promise of displaying the products of recent volcanic eruptions; but as shown below it affords evidence of an antiquity nearly as great as that of the rest of the island, although there are reasons for believing that its eruptions took place during the last stage of the emergence.
Naivaka is connected with the adjacent relatively little elevated part of the main island by a low and narrow neck a little less than a mile in breadth. In its highest part, where it is only raised between 20 and 30 feet above the sea, this isthmus is formed of the basic volcanic rocks of the district; but about three fourths of its width are occupied by mangrove-swamps which are especially extensive on the south side.
Viewed from some miles to the eastward the mountain has a regular conical outline; but from the south, when seen from Ruku-ruku Bay, it has an elongated and a much more irregular profile, descending rapidly on the east side, but displaying a gradual and a fairly regular slope of about 10 degrees on the west side. The upper part of the mountain is in the form of a curve with the concavity facing south, the crest being more or less broken up into five or six peaks showing often precipitous and at times vertical rocky faces having a drop of from 100 to 300 feet, the highest peaks ranging from 1500 to 1658 feet above the sea.