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exposed to the air, the former base alone is at first deposited, and the magnesian carbonate is only separated by evaporation. When carbonate of soda is added in small quantities to a liquid, such as sea water, containing chlorides of these two bases, the precipitate formed in the cold consists chiefly of carbonate of lime, and the liquid, by evaporaration, deposits a large quantity of carbonate of magnesia with a little lime, and then contains only chloride of magnesia (with soda salts) in solution. It is well known that the precipitate formed by carbonate of soda in a solution of chloride of magnesium is soluble in an excess of either of these salts. We have in Canada a great number of saline springs, which rise from Lower Silurian rocks, and appear to be formed by the mingling of the bittern-like waters, destitute of earthy carbonates, and derived from the lower limestones, with the carbonated alkaline waters of some of the associated strata. These saline springs, such as Plantagenet, St. Léon, and Sainte-Geneviève, deposit by evaporation, at a gentle heat, large quantities of earthy carbonates, of which the carbonate of magnesia forms from 50 to 95 per cent.; they sometimes contain but a trace of carbonate of lime. The spontaneous evaporation of basins of similar waters would give rise to the formation of dolomites or magnesites which would assume the form of detached or interrupted beds or lenticular masses among the pure limestones and other non-magnesian deposits of the region. Such are precisely the conditions in which the magnesian rocks occur in the Hudson River Group. Many of them may, however, be the result of a direct precipitation which may take place in deep sea water, from the infusion of alkaline carbonates.

Mingled as these magnesian deposits naturally are with sand and clay, we have in the silica, magnesia, lime, alumina, and oxide of iron of the sediment, the elements of serpentine, talc, pyroxene, hornblende and chlorite. For the production of these minerals it is necessary to dissolve the silica, and cause it to unite with the bases present, expelling the carbonic acid. The agent in this reaction has doubtless been an alkali. A solution of carbonate of soda at 212° F. will slowly dissolve silica, even in the form of quartz, and the silicate of soda thus formed, is at once decomposed at this temperature by the carbonates of lime, magnesia, or iron, with the production of a silicate of these bases, and the regeneration of the alkaline carbonate, which is then free to operate upon a new portion of silica. In this way a small amount of alkali may serve as the medium for the silicification of a large amount of carbonates. I have verified all these reactions by experiment, and have found that a silicate of magnesia is formed when quartz is boiled with carbonate of magnesia, and a solution of carbonate of soda.

A silicate of protoxide of iron, unalterable in the air, may be formed by an analogous process. The reactions of alumina, and of silicate of alumina under similar conditions have yet to be examined.

It appears to me that by this extension which I have given to the reaction between carbonate of lime and soluble glass, already pointed out by Kuhlmann, we have a key to the mode of formation of most of the silicates of the metamorphic stratified rocks. The subject will be found still farther developed in the forthcoming Report of Progress of the Geological Survey.

NOTES ON THE NATURAL HISTORY OF NEW ZEALAND.

BY S. P. STRATFORD, M.D., OF AUCKLAND, NEW ZEALAND.

Read before the Canadian Institute, 28th February, 1857.

Having been fortunate enough to secure a favorable opportunity for transmitting a package to Canada, I have availed myself of it to forward, for the Museum of the Canadian Institute, some specimens of the geological formations and objects of natural history belonging to this part of the world, which I hope may possess some interest for the members of the Institute.

Among the geological specimens will be found vesicular scoriæ, lava, volcanic ashes and cinders. These abound in almost all parts of New Zealand, and in the neighbourhood of Auckland are particularly marked. Auckland, indeed, is a spot especially favorable to the study of volcanic action, and I only regret that professional engagements prevent my paying such attention to the subject as I would wish. It may not, however, prove unacceptable, if I accompany the specimens with a few remarks upon the subject, or at least note, for my Canadian friends, some facts connected with the traces of volcanic action in this neighbourhood.

In the immediate vicinity of Auckland we have volcanic cones of various dimensions, from the height of a few feet to upwards of one thousand feet. They are grouped together in clusters, so that from the top of Mount Eden, two miles from this city, eighteen or twenty may be counted. It must not, however, be imagined, that the vol

canoes in the immediate vicinity of Auckland are the highest. Tongeraro, an active volcano in the centre of the island, is extremely high, rising far above the level of the perpetual snow line. It is in almost continual action, and is surrounded by mountains with altitudes approaching its own, and which exhibit clear indications of a volcanic origin; indeed, the whole country shows that the volcanic influence is general, and I imagine that the incandescent material approaches the earth's surface in an unusual manner. Solfataras, or volcanic vents, are met with, and accompanying these, abundant exudations of sulphur, of nitrate of potash, &c. Hot springs and mineral waters abound; indeed, the hot springs of Rotumakana, at which the natives cook their food, and which, from their volume, are more like cataracts than springs, fall into Lake Tampo, and heat the waters of the lake for a considerable distance around. I do not doubt that these remarkable springs will hereafter become objects of no slight interest to the geologist.

Sulphur springs are numerous, and an efflorescence of sulphate of alumina is found spreading over extensive surfaces of the earth, while the volcanic fire, which I imagine to be the remains of an enormous lava current not yet cooled, is so near the surface that a red heat may be seen in the interior, through openings in the earth; indeed, it is said that the crust sometimes breaks through, and exposes a considerable extent of burning matter. Sometimes bogs or swamps of boiling water are met with, covered by a thin crust of earth. A short time since a Missionary travelling in this volcanic region of New Zealand, ventured to cross such a surface. He broke through into the scalding water, and had his extremities dreadfully injured. It would take a long time to investigate all that is novel and interesting in this part of the country, as it is covered by an interminable forest of great density, such as a tropical climate could alone equal. It is characterised by dense vegetation, and with an immense number of climbers and vegetable parasites of great and varied luxuriance.

Auckland is distant some 500 or 600 miles from the mountain region of New Zealand; and as I have not yet penetrated to that elevated district, I cannot speak of it from personal observation. But as the Waikatu river, which rises in Lake Tampo, takes a northerly direction for 300 miles, emptying itself into the sea on the west coast of the Island, and as settlements have already been commenced along its shores, which are in direct connection with Auckland, the time is not far distant when a visit to the highlands of New Zealand will be

mainly included in a pleasure trip up the Waikatu river in a steamer. The whole valley of the Waikatu is of the most luxuriant description, abounding in excellent pasture lands; admirably adapted for grazing, and holding out many inducements to the agricultural settler.

As I have before mentioned, some eighteen or twenty volcanic cones or craters of eruption may be counted within a few miles of Auckland. Taking Mount Eden as an example; it is about 800 feet high, with a crater 300 feet deep and from 400 to 500 feet wide. The upper part consists of very light ashes, its lip is very uneven, while hillocks of ashes may be seen at different points around it. The unevenness of the lip of the crater would seem to be caused by the influence of the wind, the deposits occurring on the points towards which the wind generally blows. In some instances it would appear to depend on the sudden cooling and falling in of the lava current, as I find that the depression of the lip is often immediately over the direction which the lava took when it forced its way through the sides of the crater.

Judging solely by their external appearance, some of these cones appear to be only mounds of volcanic ashes, being flat or nearly so on the surface, but as they are distant from any other rent, and surrounded by lava and other indications of volcanic action, their true origin cannot be doubted. In some cases the craters are filled with water, forming beautiful little lakes.

I find that the lava currents of Mount Eden have taken for the most part a N. E. or N. W. direction; when they forced their way through the ashes they ran down the sides and spread themselves over the country, leaving at these spots a marked depression of the crater lip. I think I can distinguish several distinct layers of lava, and one has evidently preceded the other by a considerable period; thus the hard stony matter may be observed to have exuded in a certain direction, ending in some instances in a rounded surface, in a manner that—to use a homely simile-reminds one of hasty pud. ding which has almost ceased to run; a surface that has begun to cool and solidify, but is yet pushed forward by the fluid beneath. The more general appearance of the lava currents, however, is a surface broken up, cracked and split in all directions, the leaves are extremeuneven, and we find rugged surfaces of rock piled on each other in extreme confusion. The lavas about Mount Eden are of a blueish gray colour like trap, as will be observed in a specimen which I have sent. At the extremity of the lava current there is generally

found a stream of water, in which most commonly splendid watercresses abound, along with many beautiful aquatic plants which remain green throughout the year. Among them may be mentioned the celebrated Rapo or Typha augustifolia, which is used by the natives and by new settlers as a convenient building material. They form the walls and roofs of their houses of bunches of it, and tie them together with the Mangi-mangi or climbing fern, Lygedium articulatum. Very warm and convenient houses are thus constructed, impervious to rain or wind. I have seen the inside lined with cotton, aud then covered with figured paper; and thus finished it is exceedingly comfortable, and makes a very respectable appearance.

The New Zealand flax, Phormium tenax, grows on the margins of the streams, its leaves often measuring six feet in height, surmounted by the flowers on an elevated foot stalk. Its dark green leaves and its tuft-like appearance render it a most graceful object. Again the observer will meet with a cluster of the New Zealand fern tree Cyathea medullaris, the noble palm tree, Areca sapida, or the curious grass tree, surmounted by tall luxuriant ferns. These present a pleasant picture, a combination of grace and beauty not to be surpassed, I believe, in any other part of the world.

In the layers of volcanic matter I could easily count three successive streams of lava which are now piled one above the other in wild confusion. These eruptions tended towards the N. E. Towards the N. W. the expanse of erupted matter is more extended, rugged and broken, but does not appear to be the result of so many distinct volcanic actions. If the course of the lava current is traced, it sometimes appears to dip, or penetrate the earth for certain distances, again appearing upon the surface. In some instances a smooth dome like surface of the lava will be met with which has cooled without fracture. This presents unmistakeable evidence upon its surface of having flowed slowly, or cooled as it flowed, for marks like wrinkles may be observed, on percussion it sounds hollow, and it has plainly been a spot where the fluid lava was arrested for a short period and its surface cooled, while the internal fluid lava continued its course to the lower levels of the plain, At other points in the same current it may be observed that these domes have given way, and now form deep, rugged and dangerous cavities into which animals sometimes fall, and can seldom get out without assistance, although they may penetrate to some considerable distance along the course of the current. Some of these cavities contain water, and in many instances they are almost concealed by the thick foliage and beautiful ever

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