176 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



rocks, wliicli are mostly porphyritic trachytes of a liglit-gray color, 

 contain a considerable percentage of lime, and some of the pieces I 

 obtained were coated with crystals of calcite. To the west of the hills 

 there are high volcanic peaks on the summits of the hills, whose eleva- 

 tion is considerable. To the east, bordering Gardiner's River, there is 

 a remarkable wall, composed of limestones and sandstones, capped with 

 a layer of basalt. Indeed, the whole valley is shut in by high hills. In 

 New Zealand there is a hot-spring formation which resembles this very 

 much in appearance, although the constitution of the sediment is differ- 

 ent. In New Zealand silica predominates; here carbonate of lime 

 appears in the greatest quantity. The white deposit contains — 



Carbonate of lime, 

 Chloride of calcium, 

 Carbonate of magnesia, 

 Carbonate of strontia, 

 Carbonate of soda, 

 Carbonate of potassa, 

 Sulphate of magnesia, 

 Sulphur, 

 Silica. 



I insert Hochstetter's description of the New Zealand formation, to 

 show how similar it is in appearance : 



" First of all is Te Tarata (signifying tatooed rock) at the northeast 

 end of the lake, (Rotomahana,) with its terraced marble steps projecting 

 into the lake, the most marvelous of the Eotomahana marvels. About 

 80 feet above the lake, on the fern-clad slope of a hill, from which in 

 various places hot vapors are escaping, there lies the immense boiling 

 caldron in a crater-like excavation with steep, reddish sides 30 to 40 

 feet high, and open only on the lake side toward the west. The basin of 

 the spring is about 80 feet long and 60 wide, and filled to the brim with 

 perfectly clear, transparent water, which in the snow-white incrusted 

 basin appears of a beautiful color like the blue turquois. M the margin 

 of the basin I found a temperature of 183° F., but in the middle, where 

 the water is in a constant state of ebullition to the height of several 

 feet, it probably reaches the boiling-point. Immense clouds of steam, 

 reflecting the beautiful blue of the basin, curl up, generally obstructing 

 the view of the whole surface of water; but the noise of boiling and 

 seething is always distinctly audible. The reaction of the water is neu- 

 tral ; ithas a slight salty, but by no means unpleasant taste, and pos- 

 sesses in a high degree petrifyiug, or rather incrusting qualities. The 

 deposit of the water is like that of the Iceland springs, siliceous, not 

 calcareous, and the siliceous deposits and incrustations of the constantly 

 overflowing water have formed on the slope of the hill a system of 

 terraces, which, as white as if cut from marble, present an aspect which 

 no description or illustration is able to represent. It has the appear- 

 ance of a cataract plunging over natural shelves, which, as it falls, is sud- 

 denly turned into stone. 



" The siliceous deposits cover an area of about three acres of land. For 

 the formation of those terraces, such as we see them to-day, doubtless 

 thousands of years were required. Forbes, judging by the thickness 

 of the siliceous deposits on the great geyser of Iceland, which he esti- 

 mates at 7G2 inches, and by the observation that an object exposed to 

 the discharge of the geyser- water for the space of twenty-four hours 

 is covered with a sheet of paper thickness, has calculated the approxi- 



