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§ 35. Gilding Metal.--Alloys of copper and zinc contai and so-cal upwards of 80 per cent of copper have a reddish-yello red tint, and are used as a base for gilding. The nearly the colour approaches to that of standard gold more highly is it appreciated for articles which are sequently to be gilded. When such metal is required rolling into sheet, it will be seen by reference to the collated for the U.S. Board that the most malleable is represented by the composition, 83 copper and 17 These alloys are also known by the name of red-brass, as the reddish cast of colour is more agreeable to the than that of yellow-brass, they are frequently used for articles not requiring special hardness and strength. I the reputation, however, of tarnishing quicker than ordi brass. The properties of red-brass may be modified to special cases by the addition of tin, lead, and iron, the a of which has been already explained.

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The following varieties of brass are distinguished the preceding alloys by a characteristic yellow colou contrasted with red brass.

§ 36. Hamilton's Metal, Chrysorin, and Mosaic

Hamilton and Parker in 1826 claimed for the 50 cent alloy that, after casting in the mould and coolin exhibits the colour of gold, and does not tarnish by exp to air, even in the neighbourhood of the sea. They prep it by fusing together equal parts of copper and zinc crucible at the lowest possible temperature, stirring stantly, and then adding a further quantity of zinc in portions, till the right colour was obtained. This all very flexible when strongly heated, but not adapted for rolling or wire drawing. It melts at a comparatively temperature, and is used as a hard solder. The h alloys given under the above names are malleable and du and, as before mentioned, well adapted for cast

The method of preparation described b Parker would be quite unsuitable for adopt scale, for independently of the great wa composition of the alloy would be of an un The usual plan is to melt the copper first a zinc. The following plan has been reco open to serious objection for the same reaso above. Bring into the crucible one-half o used; place upon this the copper, and f under a cover of borax, at as low a tempera When the contents of the crucible are liquid half of the zinc (cut into small pieces) unti and throw it into the crucible in portions; effect as intimate a mixture of the metals as

§ 37. Prince's Metal.-A name given alloys varying from 60 to 75 per cent of c 25 per cent zinc.

§ 38. Bobierre's Metal. This is ordi sisting of 66 parts copper and 34 parts zinc. duced this alloy as especially suitable for shi

§ 39. Macht's Yellow Metal is compo copper and 43 parts zinc. It has a reddis malleable when rolled hot, but not in the c to be suitable for fine castings, as it possesses

BRASS CONTAINING IRON

§ 40. Many samples of brass and bron ancients have been found on analysis to co probably they knew that the addition of iron would increase their hardness and strength, it with that view. In more modern times t of iron with brass has engaged the attention o and several alloys, containing iron as an essent have been introduced from time to time. Keir proposed an alloy of 10 parts iron, w

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copper and 75 parts zinc. Similar alloys to this,
containing less iron and different proportions of copper
zinc, were introduced under the names of "sterro-meta
"Gedge's alloy," and "Aich's metal.' Sir John Ande
late superintendent of the royal gun factories, carried o
series of experiments with brass containing iron, and obta
some good results. The increased strength and hardne
such alloys were acquired at the expense of ductility
toughness. The great difficulty the above experim
had to contend with was the uncertainty in the prope
of the alloys containing iron.

§ 41. "Sterro-metal" consists of 60 parts co 38 to 38.5 zinc, and 2 to 1.5 iron. It was recomme as an alloy for sheathing for ships and other objects w are subjected to the continued action of sea-water. presence of iron in this alloy imparts to it a strength to that of mild steel, and superior to that of wroughtBrannt mentions a case in which a wrought-iron pipe b with a pressure of 267 atmospheres, while a pipe of st metal stood the enormous pressure of 763 atmosp without cracking. This alloy also possesses great elasti and is therefore specially adapted for hydraulic cylin Such cylinders, when subjected to very high pressures, b to sweat, the water from the inside permeating the por the metal. With sterro-metal the pressure can be r considerably higher than with iron or steel, without mois appearing on the outside of the cylinder.

Sterro-metal can be made very hard and dense by suit mechanical treatment, which has as great an influenc modifying its properties as has the chemical composition. rolling or hammering this alloy when hot, special ca requisite in regulating the temperature to which it is ra as by too much heat it becomes brittle, and cracks under hammer, or between the rolls. Baron Rosthorn teste sterro-metal containing copper 55-04, zinc 42.36, tin C and iron 1.77 per cent, which gave the following results

I

The tenacity of ordinary gun-metal is giv The specific gravity of the alloy was from forged or drawn into wire. Another all source contained copper 55, zinc 41 34, and

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§ 42. Aich's Metal. This alloy is an metal, and shows similar variations in various analyses that have been made. are hardness and tenacity, the same rem this as to sterro-metal, with which it is pra Alloys under this name contain from 0.4 t iron. It has a golden-yellow colour, and for articles exposed to sea-water. The f will give an idea of the composition:

§ 43. Delta-metal. This alloy was bro Alexander Dick in 1883, and since that tim a useful place for itself among modern bra "delta" was given to it by Mr. Dick, simply f connecting it with his own name, delta bein the letter D, the initial of the inventor's sur

As already mentioned, the great difficult mentalists had to contend with, was the un properties of the alloys containing iron, and himself the task of ascertaining the cause prepared various quantities of the alloy, appar

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the same way, by dissolving wrought-iron in molten copp
The results showed many discrepancies, because the amo
of iron dissolved in each sample was far from uniform.
then tried to find a method by which he might be enabled
introduce a known and definite quantity of iron, and succeed
by dissolving iron in molten zinc to saturation, and add.
the same, with or without pure zinc, to the molten copp
But when the metals were remelted, oxidation took pla
and the castings again varied in character, owing to
oxides thus formed dissolving in the alloy, and diminish
its strength and toughness. This second difficulty was ov
come by adding a small percentage of phosphorus in combi
tion with copper.
In some cases Mr. Dick also introdu
tin, manganese, or lead into the alloy, to impart spec
properties to it. The various alloys thus produced are n
manufactured and sold under the name of "delta"-met
The inventor claims that by his process the iron is chemica
combined in the brass and bronze, as proved by the all
not rusting when exposed to moist air, and by their indiffere
to the magnetic needle.

In a lecture by Mr. Macintyre before the Balloon Soci on 15th November 1889, he states that "the propert which are combined in delta - metal great strength a toughness, durability, resistance to corrosion, and a compa tively low price-render it of the greatest value for purpo of construction generally; and more especially for sh building, marine engineering, and sanitary work. It can equally well cast as forged, stamped and rolled hot, a drawn cold."

The power of delta-metal to resist corrosion by the a liquors of mines has been proved by the Bonifacius C Mining Company of Westphalia. The Company made a ser of experiments with a view to finding the relative corrosion metals of suitable strength. Brass and gun-metal were strong enough, and trials were made with steel, iron, a delta-metal. Rolled bars of each of these were immer during a period of six and a half months in the water issu