As above remarked the hot springs did not come under my notice in all parts of the island. They are to all appearance wanting in the western or Mbua portion, and also in the Undu portion north of Natewa Bay. Taking the first-named region, it will be noticed that no hot springs are indicated in the map west of the Ndreketi and Wainunu rivers. I made inquiries wherever I went, but with no result. On my writing to Mr. Wittstock, of Mbaulailai, who is well acquainted with the Mbua peninsula, he informed me that if hot springs existed in that part of the island he would probably have known of them. In that portion of the island which ends in Undu Point I could neither discover nor hear of any thermal springs east of Lambasa on the north side, and of Lakemba on the south or Natewa Bay side; nor could Mr. Bulling, who has resided at Undu Point for many years, tell me of any springs in his neighbourhood.
On looking at the general map it will be observed that the hot springs are confined to the area of basic rocks, although they do not occur all over that area, not being indicated in the map to the west of the Ndreketi and Wainunu rivers. They are not known to occur in the region of dacites and acid andesites, as in the case of the Drandramea district; and they have not been found in the area of rhyolitic and trachytic rocks that extends from Undu Point to Mbuthai-sau on the north coast and to near Tawaki on the Natewa Bay side. The region of hot springs would be limited on the east by a line joining the Mbati-ni-kama springs with those of Nandongo on the Wainikoro river and Natuvo on the north shore of Natewa Bay. Such a line, though lying within it, roughly indicates the limit between the regions of basic and acid rocks.
The situation of the hot springs in the lower levels, and their non-discovery at elevations exceeding 300 feet above the sea, are facts of importance. In more than half the cases they arise close to and often on the banks of streams and rivers, occasionally indeed at the river-bottom; and no doubt numerous unknown thermal springs issue under water from the river beds. In about a third of the known cases the springs come up on the coast between the tide-marks, usually rising through the reef-flat. At times even they are to be observed below the low tide level; and one can scarcely doubt that there are a large number of undiscovered springs that are never exposed at the lowest tides. It is also very likely that a number of hot springs issuing between the tide-marks are still to be discovered without much difficulty.