HuTTON. — The Earthquake hi the Avmri. 271 



The main range of the Spencer Mountains is formed by 

 contorted sandstones and slates, which to the west are fol- 

 lowed 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 niudstones form the 

 lower ranges surrounding the Hanmer Plains, the only known 

 eruptive rock being a small syenite boss at Hurunui Peak and 

 the Mandamus Eiver. These sedimentary rocks are of car- 

 boniferous 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 Eiver 

 Pahau enters the Hurunui Plain ; (2) at Lyndon, about nine 

 or ten miles due east of Hanmer Hot Springs ; and (3) up the 

 Mason Eiver, on the Highfield Station, about five miles east of 

 the last. 



The Hanmer Hot Springs occur on a clay teiTace 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 

 Gin. or 7in. thick, with tough clay on each side, was found. 

 This layer would pass about 10ft. or lift, under the bath- 

 house, and probably some loft. belov>' 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 alkalme 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 car- 

 bonates with the disengagement of sulphuretted hydrogen : 

 some of the latter may, however, be derived from the albu- 

 minoid 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 



