The main range of the Spencer Mountains is formed by contorted sandstones and slates, which to the west are followed by a narrow band of micaceous schists. Beyond these granite forms a range called the Victoria Mountains, which is parallel to the Spencer Mountains. East of the Spencer Mountains, much-jointed sandstones and mudstones form the lower ranges surrounding the Hanmer Plains, the only known eruptive rock being a small syenite boss at Hurunui Peak and the Mandamus River. These sedimentary rocks are of carboniferous and triassic age, some, perhaps, being jurassic. Bordering them on the north side of the Hurunui Plains, and stretching north-west towards Kaikoura, tertiary limestones, sandstones, and clays are found, which are of oligocene and miocene age, and among them volcanic rocks, not younger than miocene, occur in three places—(1) Where the River Pahau enters the Hurunui Plain; (2) at Lyndon, about nine or ten miles due east of Hanmer Hot Springs; and (3) up the Mason River, on the Highfield Station, about five miles east of the last.

The Hanmer Hot Springs occur on a clay terrace on the north side of the plain, and are at a height of about 1,200ft. above the sea. There are ten springs, two of which are cold, the rest warm; the hottest having a temperature of about 117° F. In cutting a ditch for laying pipes to take away the overflow from the baths, a layer of black peat, some 6in. or 7in. thick, with tough clay on each side, was found. This layer would pass about 10ft. or 11ft. under the bathhouse, and probably some 15ft. below Spring No. 1. One of the springs (No. 9) often brings up small fragments of this peat; so that it probably spreads under the whole. Complete analyses have been made of the water from three of the hot springs by Professor Bickerton. They are all alkaline. The salts in the springs are chiefly sodium-chloride, but in addition there are alkaline sulphates and carbonates in about equal quantities. The ammonia and albuminoid ammonia are no doubt derived from the layer of peaty matter which the waters pass through; and, no doubt also, this organic matter reduces part of the alkaline sulphates to the condition of sulphides, which are decomposed by the action of carbonic acid derived from the peat, and changed into alkaline carbonates with the disengagement of sulphuretted hydrogen: some of the latter may, however, be derived from the albuminoid ammonia. The passage of the water through the peat-bed is too rapid to allow of the whole of the sulphates being changed into carbonates; but in all probability no carbonates and no sulphuretted hydrogen, and certainly no ammonia, exist in these waters below the peat-bed. The heat of the water makes these reactions go on energetically, but the reactions

do not themselves give rise to sufficient heat to heat the water. The water must be hot before it reaches the peat-bed.^*

I mention these details because it has been supposed that the presence of sulphuretted hydrogen in these springs indicates the presence of volcanic energy below the Hanmer Plains, which has been supposed to be connected with the origin of the earthquake.

Other hot springs occur in Cow Creek, a branch of the Edwards River;^† in Cannibal Gorge; in the Upper Hope; in