36. Roundway Down, near Devizes, Wilts. 71. Cestersover, near Rugby, Warwickshire.

The preparation of Cobalt and its Oxides, has always possessed a considerable degree of interest for those engaged in the study of Chemistry: greater perhaps than its relative importance to other branches of manufacturing industry would appear to warrant. This perhaps is in part owing to the difficulty which has always been experienced in obtaining correct information, from the limited number of persons practically engaged in the manufacture, by which a subject, in itself really very simple, has been wrapped up in a kind of mysterious secrecy; and partly also, perhaps, from exaggerated ideas of the scarcity of cobalt ores, and the value of the products derived from them. Believing that an authentic account of the process by which cobalt and zaffer blues have been prepared for the use of the earthenware manufacturers may not prove unacceptable, I have been induced to attempt to describe it; and however trifling may be the actual value of the information which I can communicate, it may at least be relied on, as being derived from a practical knowledge of the business in which I myself, as well as my late father, have been engaged at Sutton Heath, near St. Helens, during the last thirty years.

I need scarcely observe, that the metals which I shall frequently have occasion to mention, namely, cobalt and nickel, were from their apparent worthlessness and intractability, objects of dislike and even dread to the earlier miners and metallurgists, who applied to them the names of some among those goblins with whom the German imagination, ever keenly alive to the supernatural, peopled the dark recesses of their mines. Cobold still figures as a malicious fiend in the legends of the Hartz mountains, and Pelz Nickel is I believe, a kind of Puck, or Robin Goodfellow, rather mischievous than really malevolent, in the German nursery tales. The application of cobalt to the arts dates from a much earlier period than that of nickel, which has only been sought after and become valuable since the introduction of the so-called German silver, of which it forms the principal and characteristic ingredient.

Cobalt is extensively employed in two distinct branches of manufacture. One application, and perhaps its most important, is to the purpose of making smalts, a well known article, consisting of glass coloured blue by cobalt or its oxides, finely ground, and extensively used in the paper and linen manufacture. The other is to the purpose of printing and painting blue on china and earthenware. Into the former of those processes it is not my province to enter, and I shall therefore confine my observations to the latter, with which alone I am practically conversant.

Three descriptions of ores are recognised by cobalt refiners in England. One called cobalt ore, obtained for the most part in Sweden and Norway, has usually been freed abroad from a considerable portion of its stony matrix by washing, but has not undergone any further preparation. It occurs of various strength or richness, and being mineralized for the most part with large portions of arsenic and sometimes sulphur, requires to be roasted previous to its reduction. Another description of ore called "zaffer," may be considered as being already in some degree a manufactured article. It is imported from Saxony, in casks containing each one centner or Saxon cwt., of various qualities, each distinguished by its appropriate mark and letter. The quality known as FFS is that most frequently employed by the refiners. It is in the form of a fine powder, has been subjected to preliminary roasting, and is professed to contain a uniform per centage of cobalt. The third division consists of ores imported in the precise condition in which they are dug out of the earth. Cobalt has been found in Sweden and Norway, in Saxony, Hungary, Bohemia, and many other of the so-called German States, in the Asturias in Spain, in Cornwall, and more recently in various parts of America. The Saxon, Swedish and Norwegian are however those most frequently employed by blue refiners, and as a general rule it may be stated, that the Saxon zaffers contain cobalt, iron, arsenic, nickel, and bismuth; and the Swedish and Norwegian cobalt, iron, arsenic, and copper, but without bismuth. In consequence of the extreme difficulty of perfectly separating cobalt and nickel, and presenting the former in an entirely isolated form, the colour prepared from ores in which the latter metal was not present was usually superior to that made from those which originally contained it, and hence the distinction, even yet, under a greatly improved process, very difficult to eradicate from the minds of the earthenware manufacturers between what are termed cobalt

and zaffer blue. Both are however the same article, but the pure oxides are usually termed cobalt, and when fluxed by the refiner previous to sale, that is, vitrified with a certain portion of flint and other materials to diminish their strength and present them for consumption in a cheaper form, they are usually, but without reason, called zaffer blues.

The processes employed for the refining of zaffer and cobalt ores being in most respects similar, I will adopt the former as the basis of my description, and notice incidentally those points in which they vary.

The first process is to reduce the ores to a metallic form, or as it is technically termed, to "run them down." This is performed in a reverberatory furnace called the "running down kiln." That which I have employed for many years is twelve feet long, eight feet wide, and five feet high to the centre of the arch. It is heated by five mouths or fire places, has two chimneys, and is capable of running down from fifteen cwt. to a ton of ore. Pearl ashes and wood charcoal are still I believe used by many refiners in Staffordshire for the purpose of reduction, but for some years past I have advantageously substituted soda ash and pulverized pit coal. These materials are not only cheaper, but the reduction is more perfect, and the produce, especially of bismuth, larger than under the old system. The mixture which I now employ is as follows :—

Three casks of zaffers, each containing a Saxon centner, is the quantity usually mixed at once. They are emptied into a wooden trough called the mixing frame. To these are added, 132 tbs. of soda ash, containing fortyeight per cent. of alkali, 54tbs. of pulverized pit coal, and 100 lbs. or 120 lbs., or thereabouts, according to the quantity on hand of what is termed "bottling scoria," from former workings, and which will be hereinafter described. The whole is well mixed with spades, and filled into crucibles of unbaked fire clay, sixteen inches high and eight wide. Fifteen casks are usually run down at once, and will fill from 90 to 100 such crucibles. These are placed in close juxtaposition on the floor of the running down kiln, and slightly bedded in sand. The fires are lighted about six o'clock in the evening, the mouths again filled up with slack or small coal about midnight, and allowed to burn slowly all night. moisture contained in the materials, which might cause the crucibles to split and run out. About six o'clock the next morning the mouths are again filled up with coal, or rekindled if extinguished, and the heat is

This is to dissipate any