GLACIERS AND GOLD.

Grey River Argus, Volume IX, Issue 617, 30 December 1869, Page 1 (Supplement)

GLACIERS AND GOLD.

Mr Ashcroft, M.P.C. for Oamaru, Otago, delivered a lecture on the above subject to a very fair audience in the Mechanics' Institute, Oamaru, lately. The lecturer stated that he proposed to divide his lecture under two heads, viz. : —(1) What is a Glacier / and (2) What have Glaciers to do with Gold '? A glacier was, then, a vast field of ice, or solid mass which formed in the valleys between mountain ranges, and having a motion proper to itself, from the expansion of its bulk by heat and other causes, carried along with it in ita slow but almost irresistible course immense masses of rock broken from the tops and sides of the mountains between which it passed. These tremendous engines had played a most important part in altering the physical features of the globe, by scooping out valleys and carrying enormous masses of drift from place to place, thus detaching portions of the oldest strata and depositing large quantities of detritus upon the top of more recent formations. To give an idea of the nature of glacial action he would read extracts from Hochstetter's work on New Zealand, p.p. 492, 497, and 481, where the Forbes, Tasman, Hoch-, stetters, and Murchison glacier (the main source of the river Tasman) was eighteen miles in length, by a breadth of nearly two miles at its terminal face, and was the largest glacier hitherto observed in New Zealand. " For a distance of three miles this glacier is entirely covered with an enormous load of debris, so that the ice is only now and then visible in transverse and longitudinal crevasses, and in large holes 100 to 150 ft (Jeep. Owing to the great steepuess of the mountain sides, a large portion of the ice is pushed, before it can melt, over perpendicular ledges, falling down with a tremendous crash, and becoming again cemented together and forming a new glacier." The elevation of the terminal face of one of the glaciers of Mount Cook— the Hour-glass glacier, so-called from its peculiar form — was 3816 ft. The Mount Tyndall glacier — 3762 ft above the level of the sea — was described as forming an ice wall, 1300 ft broad, and 120 ft high. Now such enormous masses of ice, propelled forward, must in their course cut and tear away, with almost inconceivable force the sides of the -valleys through which they passed, and the load of detritus carried down by them must accumulate in immense quantities at the terminal point of their action. Hence it was easy to perceive that we had here an explanation ot the cause of many of the mightiest changes in the physical features of the earth in which we live. To give them .an idea of the appearance of a glacier, lie would read them the eloquent description given in his " Arctic Travels" by Lord Dufterin. Writing ot a point about a hundred miles from the Greenland coast, his lordship said : — " It was shortly after this that as I was standing in the main rigging, peering out on the smooth, blue surface of the sea, a white twinkliug point of light caught my eye, about a couple of miles off the port bow, which the telescope soon resolved into a solitary isle of ice, dancing and dipping in the sunlight. As you may suppose the news brought everybody on deck, and when, almost immediately afterwards, a string of other pieces, glittering like a diamond necklace, hove in sight, the excitement was extreme. Behind that veil of misthe says further on — I knew must lie San Mayeu. A few minutes more, and, slowly, in a manner you could take no count of its dusky hem first deepened to a violet tinge, then gradually lifting displayed a long line of coast, in reality but the vista of the mountain, dyed of the darkest purple, while obedient to a common impulse the clouds that wrapped its summit gently disengaged themselves and left the mountain standing in all the magnificence of his 6870 ft, girded by a single zone of pearly vapor, from underneath whose floating folds seven enormous glaciers rolled down into the sea. Nature seemed to have turned scene-lifter, so artfully were the phases of this glorious spectacle successfully developed. The glaciers were quite an unexpected clement of beauty. Imagine a mighty river, of as great a volume as the Thames, started down the side of a mountain, bursting over every impediment, whirled into a thousand eddies, tumbling and raging on from ledge to ledge in quivering cataracts of foam, then suddenly struck rigid by a power so instantaneous in its action that even the froth and fleeting wreaths of spray had stiffened to the immutability of sculpture. Unless you had seen it, it would be almost impossible to conceive the strangeness of the contrast between the actual tranquility of those silent crystal rivers to the violent descending energy irapressed'upon their exterior. You must remember, too, that all this is upon a scale of such prodigious magnitude that when we succeeded subsequently in approaching the spot, where with a leap like that of Niagara, one of these glaciers plunges down into the sea, the eye no longer able to take in its fluviatile character, was content to rest in simple astonishment at what then appeared a- lucent precipice of grey-grefin ice, rising to the height of hundreds of feet above the masts of the vessel." The lecturer having proceeded to describe the effects of glacial action in various parts of the globe, said that it was evident that the earth must have undergone great climatic changes, indeed, it was now almost universally conceded that every part in its turn had been subjected to an arctic climate. Sir Charles Lyell, writing on this point, said:— "The opinion has of late years been steadily gaining ground that there are satisfactory proofs of cold intervals or glacial epochs intercalated among warmer periods. There are, south of the Alps, a series of beds containing immense blocks of serpentine and greenstone, sometimes striated and polished,, and thus exactly resembling those which occnr in true glacial drift. " Sir Charles Lyell also admitted that after close personal examination he was convinced that no other hypothesis to account for these facts than that of ice action, was at present tenable. Again, in the Eocene

formation north of the Alps was an immense series of beds of sandstone and shale entirely denuded of all organic remains, some of which contained angular blocks varying from ten feet to one hundred feet in diameter. These facts clearly pointed to deposition by icebergs in a 'cold sea. Still further back, in the Cretaceous period, isolated blocks of greenstone and syenite, often with granite sand attached, occured in the white chalk of the south of England, which fact was held to indicate ice action, and consequently to imply a very cold climate, for it was now admitted that chalk was a deep-sea formation, and some of the stones found weighing from thirty to forty pounds, their presence could not be accounted for by any other means than their transport by floating icebergs. The stones themselves were of a much earlier formation than the chalk upon which they were superposed, and there was at present no other probable hypothesis to account for their position than the one he had referred to. True to his great principle of seeking in the present condition of the earth for a clue to its' past history, Sir Charles Lyell— who put forth a very beautiful theory in the former editions of his work, as to past changes having been mainly due to a different distribution of land and sea from that which now exists — after showing that water was an equaisyr of temperature, warm currents continually flowing towards the poles and cold currents towards the equator, that land surfaces in or near tropics produced heat, and ne-r the poles cold, that high mountains always produced cold, and that changes of temperature were constantly carried by prevalent winds to adjacent and sometimes even to far distant lands — said " thus the winds that blow direct from Australia to New Zealand, 1500 miles distant, melt the snows on the Southern Alps of Middle Island, and produce floods, a fact which shows how much the climate of these islands might be modified, either by an extension of the continent of Australia, or by a submergence, which should lay its hot plains and deserts under water ; in the former case the glaciers might almost disappear, and in the latter (especially if an extension of antarctic land occurred at the same time towards New Zealand) they might descend to the sea, and so deteriorate the climate, as to render the islands uninhabitable. The direction taken by icebergs greatly affects temperature, and this must depend on the direction of the ocean currents, which are themselves dependent on the distribution of the land." The lecturer closed the first part ot his subject by quoting the following passage from the works of Hugh Miller wherein the appearance and condition of the continent of Europe, when the climate was cold as that of the poles, was thus described : — "There is riot a more interesting chapter in the storybook of the geologist than that which records, in language that cannot be mistaken, the wonderful fact that the terrible temperature of Melville Island (in the arctic region) prevailed as far south as the shores of the Mediterranean, and from one extremity of Europe to the other, leaving only a small portion of the surface of the earth fit to be the theatre of life. The low-lying land 3of Great Britain in those days were submerged beneath the sea, while the higher mountainous parts, whose more important general contours were the same then as now, existed in the form of islands and,peninsulas. The sea which beat upon these restricted shores presented an appearance similar .to that which the artic ocean exhibits at the present day. During the winter months it was fixed and frozen — a solid continent of iee — over which brooded a stillness of the most dreary desolation, illumined in the day time on the verge of the horizon by the pearly lustre of the ice blink, and at night by the ghastly light of the moon and the tremulous splendotirs of the Aurora boreali3. In summer the waters were unbound, and thi3 icy covering, broken up with tremendous violence into masses of various size, forming fields, floes, and pack ice, floated hither and thither in the wildest confusion at the mercy of the winds and currents. Huge icebergs resembling churches, mantling castles, or fleets under full 3ail (carved out of alabaster) sailed majestically past with the tides, dashing into fragments against the ironbound coast with a noise like thunder, or stranded upon the numerous shoals that then approached the surface. As for the dry land, it was wrapped in eternal frost, like the higher parts of the Alps and the Norwegian mountains of the present day, the central hilly regions were covered with perennial snow, from which enormous glaciers, exactlj r like those which the tourist sees in Switzerland and Norway, flowed down to the shores, filling all the intermediate glens and valleys with their icy streams." After describing at some length the great changes which had been effected in various parts of the earth by glacial action, the lecturer, in addressing himself to the question " What have glaciers to do with gold?" said that, as far as he could remember, he believed that the theory put forward by Dr Hector to account; for the chief alluvial deposits of gold in leads, was that of a river and lake action combined. Now, he could not presume to contest with such an authority any point involving a pure question of geological science, but he might be permitted to quote authorities which went to prove that there may have beeni other influences at work than that described by Dr Hector. That the process of the bringing down of golden sands by the rivers to the lakes, and the deposit at the bottom of these lakes of the gold, owing to its greater specific gravity, in layers, was the true explanation of some of the deep leads was very probable, as also that such action was in operation in comparatively recent time — indeed, something of it might still be seen on the sea beaches, and on the banks of rivers like the Clutha, but he thought that such quiet action was insufficient to account for all the phenomena. Enormous blocks of slate rock deposited here and there, immense masses of ! quartz-drift deposited in the form of rounded hills, and differing widely from river deposits ; moraines or masses of rocks tumbled in confusion (a^ the Horse

| Range) and as he learned, distinctly visible at the Ohau, Tekapo, and Waitaki Lakes, showed the operation of some powerful agency other than that of water ; an agency which correspond . exactly with that of glacial action. Tin* original formation of the old lake basins themselves gave many indications of glacial action, combined, perhaps, with successive depressions and upheavals. He could scarcely believe that the immense quantities of shingle — mostly hard slate, such as they could see in the bed of the Waitaki and t v io plains adjoining — had ever been deposited by the action of water alone, and it would be to his mind a more satisfactory method of accounting for these by the action of large masses of field-ice and icebergs, carrying blocks of stone with them, aud grinding thum down as they went into smaller fragments. Now they all knew that the matrix, or original source of the gold, was in the Primary or Secondary rocks, chiefly in the nietamorphic schists of that period and of the Silurian age. These metamorphic schists contained veins of quartz, gold being usually found associated with this quartz, though he believed it was now admitted not always, inasmuch as gold was found in slates or schists without quartz at all. But, in order to disclose the precious metal to the alluvial miner, a process of breaking up must first have occurred, by the complete rending asunder and disintegration of the hard close-textured solid rock which would resist the action of water for ages. Thus they saw the miner engaged in. sluicing among the banks of rivers, sinking through deep beds of drift, tunnelling into drift deposited in the sides of hills— bottoming generally on the slate, but sometimes on a later deposit, \ usually called a "false bottom," but which at the time of the deposit was as true as the other. The heavier deposits of shotty and nuggetty gold were, he believed, usually found on these bottoms ; but they were all quite aware that throughout whole districts of this province one 1 could hardly put a spade in the ground and wash a spadeful of. the soil without finding some specks of gold, which had, doubtless, been quietly deposited from above, as the ice in which the broken-up rock rested was melted. Wherever then the course of the rapid current had been arrested by the spreading out of the waters into a wide and comparatively still lake — there, age after age lay the precious lead here deposited, not solely or chiefly as he believed by the forward flow of the river, but by the sinking in nearly still water of the heavy metal as liberated during the summer weather from above. Therefore, while they found richer leads in some particular line, they also found in many places gold, more or less diffused throughout whole beds and hills of drift, from top to bottom. The lecturer here described the Cromwell plain from Bendigo Gully to Kawarau Bridge, and made some remarks as to deep sinking, concluding his lecture as follows : — Thus have we had at work for us a vast crushing, and puddling, and sluicing machine, leaving a mass of auriferous wash in the great tail-races of nature for us to wash. up, and travelling as I have done over many miles of similar couutry, I am astonished at the enormous wealth of auriferous deposits lying all around us and under our feet, to afford occupation and the means of livelihood to thousands upon thousands yet to come among us. We have but just touched the surface and the very edge of these mighty deposits, even leaving out of the question the great storehouses in the hills out of which the auriferous drift has been cut, and which doubtless still contain immense masses of the precious metal. One almost begins to doubt whether gold will not become too common. It cannot be eaten, it does not wear out very quickly, and yet we are finding more and more, and ever increasing the world's stock of the precious metal. Viewing it, however, as the great medium of commercial exchange — as the great extender of our modern commerce, which is rapidly opening up year by year many fresh channels and many new fields for enterprise, we need not be afraid but that all we can get will be needed, and that an all-wise Creator has put it there for beneficent purposes, having reference to the good of the race by the diffusion of population, and the benefits of civilisation and Christianity. I can even look calmly on the influx of a large Oriental population, foreign a.s they are to us in their habits, language, aud ideas : we should treat them kindly, for they may yet outnumber us, in spite of all we could do to prevent it in our selfishness. They are God's creatures as well as we are, they will be fed and cared for as well as we are, and it is not to be supposed that a race numbering two hundred millions of human beings will be always left in a state of semi-barbarism ; and all we can do is to show our superiority (which I fear we often do not) by giv : .. s them the benefit of our enlightenment and civilisation, and by excelling them in those virtues of patience and modesty for which they are distinguished. But that the Anglo-Saxon race, which has hitherto occupied so prominent a place in the colonisation of the world is destined still to lead and to rule I see no reason to doiibt ; and here, in this Colony of ours, endowed with so many of heaven's best gifts, precious metals where the soil is not adapted to support human life, good soil where there are no precious metals, and a splendid climate, which promotes the growth of a vigorous population, it is wonderful to think how many causes have contributed to produce a country so well adapted for European races. And among these causes perhaps the most remote, and yet the most efficacious, is that agency which has disclosed and opened up to the efforts of man the auriferous deposits which are the present mainstay of our prosperity — the agency of a force generally regarded as least adapted to sustain life, viz., that of intense cold, bitter frosts, pitiless snows, and destructive glaciers and avalanches. We cannot but wonder — wonder, not only at the results produced, but at the marvellous wisdom that has controlled them. Let us imitate the man of whom the poet says — And he, himself, long gazing thereupon At last fell humbly down upouhis knee, And of his wonder made religion.