The copper is estimated to increase 50 per cent. in weight; and the brass, which is composed of two parts of copper and one of zinc, to be equal to the weight of the calamine used.

In this process oxide of zinc is reduced at a temperature below the melting-point of copper, which, being thus exposed to the action of the vapour of zinc, becomes permeated with this metal and converted into brass. Care must be taken so to regulate the temperature that the copper shall not melt, but remain diffused through the mass of the charge; for if it were allowed to melt, it would trickle down to the bottom of the pot, in a greater or less degree, and much of the zinc would then escape.

:

By exposure to the vapour of zinc, copper may be converted into brass even below the melting-point of this alloy. In illustration of this fact, the following pretty experiment may readily be made :A little zinc is placed at the bottom of a clay crucible, and covered with a layer of coarsely-pounded fire-brick or burnt fire-clay; a copper coin is then introduced and surrounded with coarse charcoalpowder; after which the crucible is closed with a luted cover, and exposed during a considerable time to a gentle red-heat. surface of the coin will by this means be converted into yellow brass, without obliterating the effigy and other characters upon it. In experiments of this kind which we have made, the surface has always had a crystalline or frosted appearance.

The

Calamine-brass was formerly used by button-makers in the manufacture of gilt buttons, which were gilt by the old process of water-gilding, i.e. by means of mercury (lucus a non, &c.)—a designation which would be more appropriate to the modern method of electro-plating. It was preferred for this purpose, because it was said to receive the gold better than brass made from spelter; and to "stand the soldering better,' to which these buttons were subjected in attaching the shanks. It was also specially used in making the wire-gauze employed in the sieves of papermakers. A thoroughly practised brass-worker in Birmingham most positively maintains to me that he can immediately distinguish calamine-brass from common brass

by the peculiar appearance of its polished surface. Why calaminebrass should differ from common brass, I do not at present understand; but that such difference actually existed when the former kind of brass was largely produced, can hardly be denied. Indeed

so impressed are some of the Birmingham brass-founders with the fact of this difference, that quite recently I know one large firm has applied to an establishment in Glamorganshire for calamine-brass. Perhaps the difference between the two kinds of brass would not now be found, if the manufacture of calamine-brass were resumed; and that which formerly existed may have depended upon inferiority in the quality of the zinc produced at that time. Calamine-brass, I believe, ceased to be manufactured in Birmingham because its price was sensibly higher than that of common brass.

I have met with a statement to the effect that a Mr. Champion obtained a patent, about the year 1818, for making brass by exposing plates of copper to the vapour of zinc below the melting-point of brass; but in the Abridgments of Specifications relating to Metals and Alloys, I do not find any record of this patent. It has been supposed that the remarkably malleable brass of Nuremberg was produced by a similar method.

DIRECT PREPARATION OF BRass.

This is effected either in crucibles, as in ordinary brass-foundries, or in reverberatory furnaces, as in the manufacture of yellow-metal sheathing. The crucibles employed for this purpose have been previously described. The zinc is gradually and cautiously added to the copper when the latter has just melted. The ingots of copper before being put into crucibles, should be heated to redness. The furnaces in use in Birmingham are about 10 inches square and two feet deep, while those which I have seen in London are round. The flue leading to the stack should be small, and close to the top of the furnace; but its size must obviously vary with the stack and other conditions. The fuel should be good coke, and not such as frequently contains a large quantity of corrosive ash. The metal, when well melted, is skimmed and poured into sand-moulds for castings of various kinds; or, when intended for rolling, into closed iron ingotmoulds, previously warmed, lightly oiled and dusted over with charcoal in the interior. In former times moulds of granite were used for casting ingot-brass. In the making, casting, and remelting of brass, there is always an inevitable loss from the volatilization of zinc, for which a due allowance is made to the founders when they deliver the metal.

The Chinese appear to be unacquainted with the art of rolling brass, and, as substitute, cast it into tolerably thin sheets. I have a specimen of one of these, rather exceeding 1-16th of an inch in thickness, which I received from my friend Harry S. Parkes, so well known in his official capacity in China. It has been analysed in my laboratory by Mr. T. Philipps, and found to have the following composition :

* Manuels-Roret Alliages Métalliques, Paris, 1839, p. 169.

Muntz's Metal. This alloy, and its application "for sheathing the bottoms of ships and other such vessels," was the subject of a patent granted to the late George Frederick Muntz, of Birmingham, in 1832. The proportions specially recommended in the specification are 60 per cent. of copper, and 40 of zinc; but these proportions may be varied from 50 up to 63 per cent. of copper, and from 50 down to 37 per cent. of zinc. Best selected copper and foreign zinc are directed to be used. The metal is cast into ingots and rolled while hot into sheets, which, when finished, are "pickled" in sulphuric acid diluted with water to free them from adherent scale, and afterwards washed in water. In the same year Mr. Muntz obtained a second patent for "an improved manufacture of bolts and other the like ships' fastenings." Precisely the same proportions of copper and zinc are claimed in this patent as in the first. In 1846 a third patent was granted to Mr. Muntz for the use of an alloy consisting of 56 per cent. of copper, 43 of zinc, and 3 of lead. In the specification it is directed that only the purest metals should be used, and that the alloy is to be cast into ingots, which are to be rolled at a red heat, and treated in other respects in the manner stated in the specification of the first patent. I am not aware whether the alloy last described has ever been manufactured and applied; but my impression is that it has not; and I shall, therefore, dismiss it from further consideration. I may state that I have succeeded in rolling brass well, which, on subsequent analysis, was found to contain not less than 8 per cent. of lead.

The theory assigned by Mr. Muntz for the application of his alloy is, that by exposure to sea-water the zinc is slowly and uniformly corroded over the entire surface, whereby the attachment of barnacles, &c., is prevented. Mr. Faraday informed me that in a specimen of sheathing formed of the alloy in question, which had long been exposed to the action of sea-water, he found no zinc remaining. Experience, especially of late, has certainly not confirmed the statement concerning uniformity of corrosive action, as much of the modern sheathing is eaten away in holes, notwithstanding the declaration of copper smelters that in the manufacture of yellow metal they employed only best-selected copper and zinc of the best quality!

Muntz's metal, or yellow-metal sheathing, has entirely superseded copper-sheathing in the merchant service, though the latter is still retained in the Navy. Its special advantages are stated to be, that it keeps the bottoms of ships cleaner and costs considerably less than copper-sheathing.

* A.D. 1832, October 22. No. 6325. Metals and Alloys.

Abridgments of Specifications relating to

+ A.D. 1832, December 17. No. 6347.
A.D. 1846, October 15. No. 11,410.

It is now generally made in reverberatory furnaces, the zinc being cautiously added to the melted copper. The melted metal is tapped into a vessel lined with clay, out of which it is laded into suitable closed iron ingot-moulds, the interior of which has been lightly oiled and dusted over with charcoal in the usual manner. Just previously to tapping, samples of the alloy are taken out, in the same manner as copper-proofs in the process of refining copper, and cast into small ingots, which are passed through rolls while still hot, and are afterwards broken across, when, if the fracture presents the proper appearance, the metal is tapped out forthwith. The fracture should be close and finely granular; but if it does not present the proper appearance, zinc is thrown into the furnace and well mixed with the alloy, after which the fracture is again examined, and if it is right, lading takes place immediately; but if not, the process of adding zinc and the testing of the fracture must be repeated until the desired quality is attained. The eye of the furnace man requires to be educated for this kind of examination. Although the proper quantities of the two metals may have been put into the furnace in the first instance, yet, from the very nature of a reverberatory furnace, it is impossible to calculate upon the precise amount of zinc which may be volatilized, even in the same furnace at different periods. Hence the necessity of testing, &c., above described. But as the usual charge of a furnace consists of copper, (( new scrap,' ," and old yellow sheathing, of which the average composition is not exactly known, it becomes all the more necessary to follow the course above described in order to produce an alloy of the right quality. I am informed by an experienced yellow metal manufacturer, that the proportion of zinc should not exceed 38 per cent.-that if it sensibly exceeds this proportion, the sheathing is apt to become friable-and that if it is sensibly below this proportion, it wears away too rapidly.

The rolled sheets, after final annealing, are immersed in dilute sulphuric acid, scoured on the surface with flannel and sand, and afterwards washed and dried.

I am assured that cast yellow metal nails of the same composition as the sheathing cannot be used for attaching it to the bottom of ships. The copper sheathing in the Navy is attached by nails having the following composition:

Mr. Muntz, like most successful patentees, had to encounter opposition on the part of certain copper-smelters, and to defend his patent-rights in the Courts of Law. He succeeded in obtaining a signal victory over his opponents, which certainly has not always been the fortune of patentees who have benefited either themselves or the world by their inventions. At the expiration

of the patent in the ordinary course of fourteen years, Mr. Muntz applied to the Privy Council for an extension of it, when he admitted, if I remember correctly, that it had yielded him a profit of not less than £68,000. The application was refused.

A

few years afterwards, Mr. Muntz died, and his property was sworn under £600,000; The manufacture of the alloy is still conducted on a very large scale near Birmingham, by one or more of his sons. There are but few if any metallurgical patents which have been so profitable to the patentee as that of Mr. Muntz. Most of the large copper-smelters are now engaged in the manufacture of Muntz's metal.

GEOLOGICAL SOCIETY OF LONDON.

At the Meeting of February 26.—Prof. Ramsay, President, in the Chair.

George Charlton, Esq., Mining Engineer, Dukinfield, Manchester, and Julius Schvarcz, Ph.D., Stuhlweissenburg, Hungary, were elected Fellows.

The following communications were read :—

1.-"On the Drift containing Arctic Shells in the neighbourhood of Wolverhampton." By the Rev. W. Lister, F.G.S.

2.-"On a Split Boulder in Little Cumbra, Western Isles." By James Smith, Esq., F.R.S., F.G.S.

The Islands of Great and Little Cumbra have (like the west coast of Scotland) a cliff and terrace, indicating an elevation of about 40 feet above the present level of the sea, and the removal of at least 100 feet of rock (sandstone and trap); the sea at its present level having worn away the rock to the extent of only a small fraction of an inch. The terrace on the Little Cumbra has been moreover ground down and scratched by ice-action, the striæ passing unobliterated under the present sea; and on the terrace lies a split boulder, such as are known to fall from glaciers, and which the author thinks must also in this case have fallen from an escarpment of ice.

3.-"On the Ice-worn Rocks of Scotland." By T. F. Jamieson, F.G.S. The author, first referring to the eroded surface of the rocks beneath the Drift-bed in Scotland, proceeded to show that the action of ice, and not that of torrents, could produce such markings, as he had observed in the bed of a mountain-stream in Argyllshire, down which had poured the torrent caused by the bursting of the reservoirs of the Crinan Canal. He then advanced reasons for considering that the erosion of the rocks in Scotland was due chieffy to land-ice and not to water-borne ice, bringing forward remarkable instances of ice-action on the glens and on the hill-sides at Loch Treig and Glen Spean, where moraines, blocs perches, striæ, roches moutonnees, and boulders lifted above the parent-rocks indicate a northern direction for the great ice-stream_from_Loch Treig to the Spean, and then an eastern course on one hand up Loch Laggan, and a western, on the other, down the Spean. Up Glen Roy, the ice had apparently passed north-eastwardly, over the watershed, towards the Spey. In Knapdale, Argyllshire, similar evidence is obtained of a great ice-stream passing over hill and dale; here falling into the Sound of Jura. The author referred to Rink's and Sutherland's observations on the continental ice of Greenland as affording a probable solution of these phenomena; and, objecting to the hypothesis either of floating ice and of debacles being sufficient to account for the conditions observed, he thought that land-ice, moving from central plateaux downwards and outwards, has effected the extensive erosions referred to, both in Scotland and other northern regions, at a time when the land was at a much higher level than at present. This must have been followed by a deep submergence, to account for the stratified and shell-bearing drift-beds.