surface of the water.

The metal is thus broken up into small fragments of fairly uniform size.

According to Krupp, the finest and most uniform product is obtained in the following manner :

"At some distance above the surface of the water, serving for the collection of the grains, a horizontal pipe is arranged which is connected either with a powerful forcing pump or a water reservoir. Before pouring the metal the cock on the pipe is opened, so that the jet of water issuing from the pipe is thrown in a horizontal direction over the vessel containing the water. Upon this jet of water the molten metal is poured. The greater the force with which the water is forced from the pipe, the greater also the force with which the stream of melted metal is divided, and by this means it is possible, within certain limits, to obtain grains of a determined size." As will be seen from the above description, the scattering of the stream of molten metal is based on the same principle as that employed in diffusing fragrant liquids in the air.

When solder is granulated by pouring into water, it is necessary to remove the grains from the vessel as soon as the operation is completed, and dry them quickly, so as to avoid unnecessary oxidation.

MANUFACTURE OF BRASS

§ 49. Allusion has previously been made to the two distinct modes of making brass, known respectively as the calamine and direct methods; the former being almost exclusively used until within the last fifty or sixty years, but is now practically obsolete, at any rate in this country. In the ancient or calamine method, metallic copper is mixed with oxide of zinc and charcoal, and the mixture strongly heated for twelve hours or more, when the zinc, reduced by the carbon and carbonic oxide present, alloys with the copper forming brass. Such brass has been claimed to be of superior quality to that made by the direct process, but as great improvement has taken place in the qualities of brass of late years, it is very doubtful, if the manufacture of calamine brass were to be resumed, whether the value of the metal for most purposes would be superior to what the market can at present command. The reputed high quality of brass made by the old method could only be maintained by exercising great care in the quality of the ore and copper employed, and selecting ores of uniform composition to produce a product of uniform and determined properties. The cost of production of calamine brass is less than that of brass made by the direct process, but the former method is much more tedious and troublesome, requiring a much longer time than is consistent with modern requirements, and for small founders is quite unsuitable.

CALAMINE BRASS

§ 50. For calamine brass the ores were submitted to a preliminary treatment in order to remove as far as possible other compounds, such as those of lead, antimony, and arsenic, which would injure the quality of the brass. Native calamine was calcined to remove carbonic acid, sulphur, or other volatile matter, and form zinc oxide. The calcined ore was then ground in a mill, any galena removed

by washing, and the dried oxide mixed with about one-third its weight of coal or charcoal, and introduced into crucibles with alternate layers of granulated copper.

The crucibles employed were made of fire-clay, 12 inches deep, 8 inches wide at the top, and 62 inches wide at the middle, inside measure. The king-pot, as the middle pot was termed, was 13 inches deep, and would hold 120 lbs. of metal, while the smaller ones would only hold 84 lbs. The charge consisted of 100 lbs. calcined ore and 40 lbs. coal, to every 66 lbs. of bean-shot copper.

1 The furnace used, Figs. 5 and 6, consisted of a circular chamber m, lined with fire-brick; it was contracted above to a circular opening, in which was fixed a cast-iron collar ee; it was closed at the bottom by a cast-iron bed-plate aa, in which were twelve holes symmetrically arranged round one larger hole in the centre k, through which the ashes and clinkers could be withdrawn from time to time. Below this plate was the ash-pit n, communicating in front by means of an air-way c, with a vault i, through which air was admitted, and access gained by the workmen to the ash-pit. In the small holes in the bed-plate were placed cast-iron twyers, tapering upwards. The space between the twyers was filled up with fire-bricks to form a solid bed. The air for the combustion of the fuel entered through these twyers. Several furnaces were constructed in a row, and the whole covered with a large cone like that of a glasshouse.

The crucibles were placed in the furnace so that the large or king-crucible occupied the central position. Each pot was loosely covered with a piece of coal, and smaller pieces of fuel were packed between the pots. When the operation was completed the king-pot was first removed, and the contents well stirred with an iron rod. Each of the side pots were then removed in succession, well stirred, and when the brass in each case had subsided to the bottom the contents were poured into the king-pot. The dross was 1 Percy's Metallurgy, p. 613.

then skimmed from the surface, and the metal poured into suitable moulds.

In this process oxide of zinc is reduced at a temperature below the melting point of copper, which, being exposed to the action of the vapour of zinc, becomes permeated with this metal and converted into brass. If the temperature be raised too high at an early stage of the process the copper would melt, sink to the bottom of the crucible, and much of the zinc escape without alloying with the copper.

When the metal obtained by the above process was not of the desired quality, it was necessary to undergo a fresh fusion with calamine and charcoal, or with copper, according as the copper or zinc was in excess.

DIRECT PREPARATION OF BRASS

§ 51. This method consists of melting copper and zinc together in the desired proportions, either in a crucible, or in a reverberatory furnace, the latter being used chiefly for Muntz's or yellow metal, where large ingots are required. Many attempts have been made to do away with crucibles for the manufacture of brass, and to substitute special furnaces of the reverberatory type; but the loss of zinc is so great, and the composition of the brass so liable to be uncertain, that even for yellow metal many manufacturers have discarded the reverberatory, and gone back to the old crucible method.

A crucible furnace is generally a rectangular chamber 12 to 16 inches square and 3 to 4 feet deep, lined inside with fire-brick, and connected near the top with a chimney by means of a flue, which is generally horizontal at the part adjoining the furnace, then inclining upwards into the chimney. This is especially the case when several furnaces open into one chimney. The proper construction of the furnace and disposition of the flues is a matter of the first importance, as a slight difference in the arrangement of the flues will considerably affect the draught and prevent the