522 Transactions. — Geology. 



are, I thiuk, a sufficient number of volcanic safety-valves — 

 two hundred and seventy to three hundred — to keep our 

 present supply of water upon the surface. The local Tongan 

 earthquakes are therefore, no doubt, connected with the 

 eruptions of Tofoa, which is a high flat-topped island nearly 

 five nailes in diameter, situated about fifteen miles to the 

 westward of the Hapaai Group, 1,890 ft. high, and is a vol- 

 cano in continual activity. But it may be — I do not say it 

 is — that this particular group of islands is affected by distant 

 earth-movements in Java and South America. We shall be 

 able to judge better, after we establish seismitic stations in 

 this most interesting position of the earth's volcanic energy, 

 whether Tofoa acts m sympathetic connection with Java and 

 Central and South America. 



I, of course, ask to be excused for venturing to express any 

 opinion, or to draw any conclusions in the course of this 

 paper, upon the facts I have observed and collected. My 

 simple duty is only in this paper to record those facts. But 

 the subject is so interesting, and the field of observation so 

 new, that it is difiicult to refrain from drawing some con- 

 clusions. I shall therefore feel favoured by members correct- 

 ing me wlieu I err, as I have not had the time to study 

 volcanology, and should like to be informed correctly con- 

 cerning the facts I have noted. 



Kao Island,' lying two miles and a half north-north-east 

 of Tofoa, is 3,030 ft. high, but not an active volcano. Captain 

 Sir Everard Home, in H.M.S. " Calliope," who visited the 

 Friendly Islands in 1852, reported that a volcano, or the in- 

 dications of one, had been perceived about half-way between 

 the Islands of Kao and Lette ; and about twelve months 

 previously smoke had been seen issuing from the surface of 

 the sea. This date approaches somewhat the great earth- 

 quakes in Wellington. 



Eeturning for a moment to Metis and Lette, I might 

 mention tliat an island of volcanic origin, about 200 yards 

 long and 110ft. high, situated in latitude 19° 11' S., longitude 

 174° 49' W., was passed by H.M.S. " Sapphire" on the 16th 

 April, 1878. It ejected quantities- of white smoke, and ap- 

 peared to be covered with sulphur. The island would seem 

 to be identical with the rock, 29 ft. high, reported by the 

 German ship " Metis " in 1875, the effects of volcanic action 

 having probably added to its size. During my late trip I 

 passed near this rock, and, as I have said, Mr. A. W. 

 Mackay informed me that it was one mass of sulphur. The 

 different estimates of height and size of this rock which I 

 have given are interesting. 



About six miles northward of Honga Tonga Island, which 

 is two miles north-east of Honga Hapaai, lying to the north- 



