Mr. Phipson, in a letter to M. Elie de Beaumont, draws attention to a specimen of native zinc now in the International Exhibition. The specimen occurs in basalt from Brunswick, near Melbourne, Victoria. It has before been stated by G. Ulrich that metallic zinc has been found near Victoria; and, according to Becker, it occurs also in the gold-washings of the Mitta River.-(H. W. Bristow.) Such cases are remarkable, it being very uncommon to find any readily-oxidized metal in the native state.

The mineral lepidolite, or lithiamica, has been used as a source of lithia. Certain varieties contain more than 1 per cent. of the newlydiscovered metal rubidium, and these form a convenient source for obtaining this element and its compounds.

Welsh gold continues to attract increased attention. It is constantly being discovered in fresh localities of the Dolgelly district, and expectation is raised to a very high pitch about the auriferous region. It is variously found in quartz, in lead, in alluvium, and in blende. Since the beginning of 1861, about 7,000 oz. have been extracted from quartz-rock in the district. The value of the precious metal thus obtained is more than £25,000, at a cost of £2,000, exclusive of the royalty of one-twelfth paid to the Crown. At Clogau, lately, no less than 142 oz. were obtained from 840 lbs. of quartz. Later accounts state that the district is now being examined by Mr. Mosheimer, commissioner from California to the International Exhibition. He pronounces the district very favourable, but condemns the mode of extraction used at Clogau. It is said he is so confident of the value of some lodes, that he has purchased large interests, sanguine of being well repaid. Explorers have now found their way to the isle of Anglesea, where there is much quartz that resembles that of the goldbearing districts.

Metallurgy. The preparation of cast-steel is attracting very considerable attention. Bessemer's process and modifications of it are fast gaining ground. It has frequently been objected to this process that it did not sufficiently or even sensibly remove the sulphur and phosphorus from the cast-iron. Mr. G. Parry, of the Ebbw Vale Iron Works, Monmouth, has patented certain improvements in the manufacture of iron and steel, one object of which is to get rid of these objectionable constituents. He takes ordinary wrought-iron and raises it to a very high temperature in a melting-furnace along with fuel and fluxes. The heat obtained is much greater than that required to melt the iron, which combines with some of the fuel, and becomes carbonized. By subsequent puddling, much of the sulphur and phosphorus are got rid of along with the carbon. If necessary, the carbonization and puddling are repeated. He thus obtains purified wrought-iron. This may be carbonized in the same manner sufficiently to convert it into hard steel. And from this soft steel is obtained, by re-melting it in a separate furnace, and blowing air through it. By these processes nearly all the pig-iron produced in this country becomes available for the manufacture of cast-steel.

An important memoir on this subject by M. Frémy, well known from his researches on the composition of steel, has been lately read before the French Academy of Sciences. He remarks that steel is growing in importance so rapidly that it is incumbent on any nation wishing to preserve

its position, to keep up with the metallurgical science of the day. In employing methods requiring much fuel, France could not successfully compete with England, and his object has been to discover processes which will place his own nation in a more advantageous position. It was formerly considered that the ores of Sweden and Russia were the only ones suitable for making iron destined to be converted into steel; and it was also believed that the iron must obtain from its ore a sort of propensity for steel. M. Frémy tried to find out from what this propensity resulted, and his analyses led him to believe that iron required not only carbon, but other metalloids, as phosphorus and nitrogen, in order to become steel. [These conclusions were at the time hotly contested in the Academy.] He came to England on the jury of the Exhibition, and saw Bessemer's process, which left doubts on his mind whether it could be applied to the comparatively impure French iron; but his experiments, conducted on an extensive scale, completely reassured him. It resulted that any iron, if sufficiently refined, could be converted into excellent steel by the necessary processes. He was able in twenty-five minutes to convert French castiron, worth about ten francs the 100 kilogrammes, into cast-steel worth 150 francs the 100 kilogrammes. He is careful to say that in every case chemical examination of the iron is necessary in order to find out what constituents require removing, and what require adding.

It is now known that Bessemer is making steel from a hematite pig-iron of the North, infinitely superior to anything ever produced on the old converting principle from the most expensive kinds of Swedish iron. Hence, as a trade circular remarks, "there is great demand for hematite pigs."

There is a belief among practical men in Germany that pig-iron which contains copper cannot be puddled; and it has been said that when one puddler wishes to annoy another, he will sometimes throw into the iron a bit of copper, such as a small coin, and that this prevents the iron from "rising." Dr. List, of America, has observed two instances which go to prove that this belief may possibly be correct. In one of these, where the puddling did not succeed, he found about 0.3 per cent. of copper.

The far-famed swords of Damascus were examples of the wonderful perfection to which the manufacture of steel could be brought, even in a long-forgotten age. The art of manufacturing them was lost for centuries. Besides their elasticity they were valued for the peculiar mixture of light and dark waves on their surface; and it was long found impossible to imitate this appearance. At present, however, blades resembling the old Damascus scimitars, equalling them in temper and elasticity, are made at Solingen, in Germany, the only establishment of the kind in the world. A faggot is first formed of alternate fine bars or wires of iron and steel. It is drawn out, doubled, and twisted several times, and then formed into a ribbon. Two such forged ribbons are welded together, enclosing between them a thin blade of the best cutting English steel. After polishing, the Solingen Damascus blade is dipped for a short time into dilute sulphuric acid, which, by rendering visible the carbon of the steel, produces the wavy surface so much desired. The combined twisted iron and steel gives peculiar toughness to the weapon.

M. Alf. Riche, in studying the difficult subject of metallic alloys, has

made use of a new method for indicating the point when a true chemical compound is obtained. He examines various mixtures of two metals, comparing their densities with that which would be expected were no combination to take place. In most cases it is found that there is a contraction; and the point of maximum contraction he considers to indicate the existence of a true alloy. By this method he determined the composition of the alloy of tin and lead to be the same as was obtained by Rudberg in a totally different manner.

Mining. The lamentable accident at Hartley Colliery, in January last, gave rise to a general belief that two shafts are required to each mine for the purposes of ingress or egress. As a result of the outcry, an Act has been passed which compels colliery proprietors to have two separate means of exit from each mine, although the two openings need not belong to the same mine. Fortunately many other dangers are lessened by the use of two shafts, so that the compulsion cannot be considered a hardship.

Many accidents have happened in coal-mine shafts from the breaking of the rope. A great variety of "safety-cages" have been invented, so arranged that if the rope breaks, a set of springs push out arms or levers which grip or wedge fast against the conducting-rods, so that the cage is brought to a stand. One difficulty, however, has arisen from the employment-now becoming very general-of iron conducting-rods, whilst most "safety-cages" were suited for wooden ones. Two or three modifications have, however, lately been brought out, which are intended especially to apply to iron rods, and we hope that they will receive all attention from the colliery proprietors.

1

PHOTOGRAPHY.

A TRIUMPH OF PHOTOGRAPHIC ART.

PERHAPS some of our readers may think that a record of the various

improvements which are made from time to time in the photographic processes would derive additional interest from a description of the results obtained by new applications to the art. Such an account would, however, fill our pages, and leave room for no other subject; for in the present day, everybody and everything is photographed. Objects which require the highest powers of the telescope or microscope for their definition are brought before our eyes in a clear and agreeable picture. Others, again, are reduced from their natural size, and the photographic image is so diminished that the microscope must be employed to render it once more visible to the eye. Some of these works of art are simply curious and interesting; others are also useful. Then, as to persons, we will not ask who is, but who is not, photographed nowadays? Indeed, we think, it will be obvious to all, that it would be impossible for us to give an account of the various results which are from time to time attained by means of photography. Nevertheless, when extraordinary instances of success are brought under our notice, such as we deem deserving of the attention of our readers, we shall at all times be glad to accord them a portion of our space.

Of these, a striking one is now before us, and it is rendered doubly interesting from its immediate connexion with the general progress of every branch of science. It is a photographic picture of twenty-two gentlemen, leading members of the British Association, who met in Manchester last year, and who are artistically grouped (mostly seated), in the drawing-room of the President, Dr. William Fairbairn.

Some of the gentlemen are personally known to us, and, judging from the speaking likenesses of these, we have no doubt that all are equally perfect. There is a total absence of all stiffness or awkwardness either in the attitudes of the individuals, or in the whole or any portion of the group. One or two appear to be speaking, the rest listening attentively, and, quite contrary to photographic precedents, all appear smiling and good humoured. What renders this still more extraordinary is, that each of the portraits was taken separately, and the picture afterwards compiled by the artist, Mr. Alfred Brothers, of Manchester.

The copy before us is reduced from the original, and is 16 inches by 9 in measurement. The original is 2 feet 9 inches by 1 foot 7, and its production involved no less than 40 separate printings! The gentlemen thus vividly portrayed are:-J. F. Bateman, Esq., C.E.; Sir R. Murchison, F.R.S.; C. C. Babbington, Esq.; Rev. W. V. Harcourt; Rev. Dr. T. R. Robinson; R. B. Darbyshire, Esq.; Sir David Brewster, K.H., F.R.S.; Alderman Neild; Professor Airy; Lord Wrottesley, F.R.S., &c. ; General Sabine; Joseph Heron, Esq.; Professor Miller; M. Curtis, Esq. (Mayor); Alderman Mackie; Wm. Newmarch, Esq.; Professors Hopkins, Sedgwick, Willis, Phillips, John Crawfurd, Esq., and the President, Dr. Fairbairn.

The price of the picture is a guinea, which is about the value of any one of the portraits, for those who take an interest in the persons photographed. The London publishers are Day and Son; Manchester, A. Brothers.

ONE of the most conspicuous and, at the same time, important results which has made itself apparent, in connection with the display of photographs in the International Exhibition, has reference to the degree of permanence attainable in these works of art, and to the dependence which may be placed upon the photographic system of record. It is an undoubted fact, that a large number of the pictures on view at the Exhibition are becoming rapidly defaced, and are showing the most unequivocal signs of fading; some of these which have suffered most have contracted a uniform yellow complexion; others, at an earlier stage, are fading in patches, and present a kind of mottled aspect; some few of the worst cases have, we understand, been altogether withdrawn by their owners from public inspection. These appearances are by no means limited to the works of one or two operators, nor to the productions of England alone; for the same indications of fading are apparent in the beautiful specimens of photography distributed throughout many of the foreign courts. Numerous instances are observable in which, among several impressions mounted together in the same frame, and subject therefore to the

same influences, a few only have succumbed to the trying conditions by which they are surrounded, the rest remaining apparently uninjured.

In searching for the primary causes which are likely to be operating adversely in all these instances, it is not necessary to look far to discover the evidence of a damp atmosphere, and considerable fluctuations in temperature, as being paramount among the causes that have occasioned so much destruction. The glass-plate in front of the pictures is frequently bedimmed with a film of dew, and the mounting cards are, like the photographs, manifestly affected by damp, several of them having become spotted with mildew; this is especially the case with the show-frames of the London School of Photography, and those of Mr. Warner, of Ross. The beautiful view of Buttermere, exhibited by Mr. James Mudd, and hanging beside the former on the same wall, is also the victim of circumstances which are plainly indicated by the growth of mildew on the mounting-card; while, strange to say, an excellent print of the South Stack Lighthouse, by the same artist, and placed contiguous, has resisted perfectly the action of moisture. The other works by Mr. Mudd are hanging chiefly on the central screen in the photographic gallery, where they are considerably less liable to be affected by damp, and have consequently preserved all the delicacy and beauty of toning for which the photographs by this gentleman have long been celebrated.

The same remark applies to the pictures exhibited by Mr. Vernon Heath; to the views in North Wales, by Mr. Henry White, and by Mr. Sidebotham; to those of Mr. D. Campbell, of Ayr; and likewise to the exquisite landscapes in Madeira, by Mr. R. M. Gordon: none of these disclose the least symptom of fading, and all are placed upon the central screens. In like manner, with regard to the portraits by Mr. T. R. Williams, and to the magnificent series of abbeys and cathedrals by Mr. Francis Bedford, not one of these shows the least indication of fading; but it must be stated that they occupy the more favoured position in the centre of the gallery.

A remarkable instance of the formation of mildew is apparent on the leather binding of a book exhibited by Mr. A. W. Bennett, and entitled "The Ruined Abbeys and Castles of Great Britain, illustrated by Photography." This book is inclosed within a glass case, and hangs directly in contact with the wall. Some few of the exhibitors appear, however, to have adopted the suggestion of Mr. G. Wharton Simpson, and have inserted pieces of cork between their frames and the objectionable wall ; the advantage gained by this precaution is already manifest by the protection afforded to these prints.

As the general conclusion, from observations made upon the photographs now on view at the International Exhibition, it must be admitted, that the security of a photographic record depends, not merely upon the amount of care bestowed originally upon its preparation, but quite as much upon its being preserved in such a manner as to exclude, as far as possible, the adverse influences of damp, or actual contact with moisture, produced by condensation on the front glass: conditions to be fulfilled which, as yet, do not appear to have received their merited share of attention.