SCIENTIFIC TALKS,

Otago Witness, Issue 1916, 6 November 1890, Page 42

SCIENTIFIC TALKS,

By N. D. C.

%• In the vicissitudes which affect; all things it is not to be expected that the articles of commerce and manufacture should be exempt. Yet it seems strange to find fluor-spar, a flux used in the reduction of iron ore, p.irtakinj? in the ebb and flow. At one time in general use, it a r.-v limply came ro be d>S;\,XC d, : -'jit iutM . iU.^.'VI ali ; /luU' i. -.-.M, j by . > nv. , !>i,i „•;.■.(,, , in' i_v v), ..y-^u.Li ji j tne 'itut'-. v" I;- 1111 ' 1 - -•'. U . js- , , ' viJ ';: j to trie U luuiike! Ztslut if-, is a present mx ur seven times that of lime, but in spite of ihat it is now gaining ground, and seems destined to again play an important part in the metallurgy of iron and other ores. One of its advantages is that its use effect-, a saving in fuel ; another that it attacks the phosphorus and sulphur, which impair the strength and quality of the iron, and carries some of them away into the slag. This great solvent or fusing power of fluor-spar is not confined in its effects to the three elements mentioned, for it also acts on the sand in the same way, forming the very tough variety of metal known as silicon iron. And, indeed, its distinguishing quality is the wideness of its application. %* The news of the discovery of rich deposits of gold in the Grand Canon of the Colorado river in quantities that will yield enormous returns cannot come upon anyone in the nature of a surprise, for, although the quantity may well be doubted, we are con siantly being reminded of the wideness of the distribution of the precious metal, occasionally rich, but usually in such small quantities as to preclude the idea of its being profitably worked. It was only lately that a project was formed to build a railway through the Grand Canon itself, on a natural bench or terrace, which runs along the steep side of the towering cliff, from 20ft to 150 ft above the level of the water. Unique as such a scheme may appear, it was expected to cost less than the other tailroads in the State which run over hill and valley. Abrupt and precipitous the sides of the canon rise in places to a height of over 6000 ft, but still, showing clearly the different slopes and grades assumed by the varying strata of limestone, sandstone, and shale, lying comparatively level, which compose the tableland through which the water has gradually cut its way. The number and length of these ravines show that this is the case, and that they cannot be due to any faults, a 'theory which is sometimes invoked to a account for mountain gorges, and which is also disproved in this case by the sequence of the strata on each side corresponding. At places these walls of the Grand Canon are miles apart, and in the broad and level valley, a second canon has been eroded in the same manner as the first. No matter how we regard the way in which this has been done the one incontestable fact i% that the eroding power of the river has greatly exceeded the disintegration of the atmospheric agencies To understand this properly, if we compare it with our own Taieri river in the part beyond Hindon which has been termed the " garden wall," we find that the soft schist, which forms the bedrock of Otago, has been unable to withstand the effects of denudation, and instead of perpendicular . Bcarps, blocks of schist of all sizes and countless number have been broken off from the cliffs through the action of frost, rain, and changes of temperature, and have themselves undergone disintegration, so that a rough soil has been interspersed among the rocks, forming a steep and usually inaccessible slope, by no means vertical, on which grows a scant vegetation of tussock and stunted trees, and "always tending to become less steep as the top of the cliff recedes; not so with the Colorado. The Carboniferous rocks which form the greater part of the strata have yielded before the solvent and mechanical action of the running water, which has gradually cut down through the tableland, but they have withstood the effects of weathering, forming Bteep escarpments of regularly stratified rocks down to the Siluiian beds or the granite, which is the basement rock of the district. The fact of gold having been found will no doubt give an impetus to tlje proposed railway, and concentrate public attention on this great system of ravines, unequalled in the world for their stupendous grandeur. *+* The silence which for a time surrounded the search for coal in the south-east of England has been broken by the address lately delivered by Professor Boyd Dawkins before the Eoyal Institution. We know that a northern coitinent existed in Primary time which included both the Highlands of Scotland and Scandinavia ; while to the south extended a large and shallow sea. The great rivers of this aucient northern land, of which the ramparts of the Grampians were the Bonthern limit, deposited their detritus in this sea, which as it gradually filled formed the mud flats on which the flora of the coal period flourished, until the movement of de-pres-ion arrested their growth. The continued subsidence of this area caused the sea to tiiumph, and the whole of the Secondary group of rocks would in the natural order of things be superimposed upon the Carboniferous; but before this took place the rocks of 'he latter period had undergone a folding movement, and the upper parts $ the folds, or anticlines, had been

eroded or denuded away, leaving the troughs with their coal seams intact. Of these folJs there is evidence from the French and German coalfields, and they have beea trace i as far as Ireland. Professor D.-Avkuis reminds us h w, following U p this* chain of reasoning, ihe idea of workable coal in the soutli-e-^t of. England had damned on the mitid of Gu'hv'u A.us'eu m l' 1"^1 "^ j>^o h^ 1*56, and how rhe " possibility " of that year hdd crown into i% prob,il>ili(y "in 185 St till this wa>- of little vsiluo on account of the possibility of an enormous thickue>s of the overlying rocks ; but observation and experimental borings established the fact that the Permian and Secondary rocks thin out to the south, the former abutting against the ridge of Artois in France. In Belgium and Westphalia, the Cretaceous rocks rest immediately on those of the coal period ; so that the only other condition wanting was that the continuity of the troughs between the coalfields of Northern France and those which exist on the extension of that line in England should prove unbroken. The Thames valley and the weald of Kent and Sussex he mentioned as likely places. The result of the recent boring at Shakespeare Cliff, near Dover, has been that the coal measures have been struck at 1200 ft, and penetrated to a depth of 70ffc, in which was one coal seam. This great triumph has only been brought about by patient research, and it just requires the coal to be presont in sufuVirtht quantities to leave the realm of th'ory and 'jims: piac-iio-il mining into play.