The casting of metals having a low fusing-point is one of those things which is well within the reach of the amateur or professional caster, provided he has certain of his alloys made for him, and he can have a range of temperature for his metals and alloys from about 96° Fahr. to about 1,500° Fahr., and for melting these an ordinary plumber's furnace or a portable forge will provide sufficient heat. As to hardness, these metals and alloys can be had from the softness of the softest solder or tin to that of cast iron, and with tensile and bending strengths up to moderate steel, and they will stand friction well, particularly when properly lubricated. Great heat they will not stand, as a matter of course; but many will stand from 250° to 400° Fahr. without injury. The cost is that of brass and bronze, if the alloying is done at home; but of course, when made out, the cost of alloying has to be considered.

Where alloys are made it is usual to melt the most refractory metal first and then to add the others according to their fusing-points, afterwards pouring into bars or slabs, remelting to secure uniformity, and then running into bars or narrow slabs, the latter - poured on edge - being about 3" wide and 1/2" thick for convenience of quick melting at a moderate heat.

The metal referred to in this paper can be cast in iron moulds, in plaster and fine Bath brick moulds, or in ordinary sand - weak loam - moulds; the system of moulding with sand or plaster moulds being the same as for brass, except that the sand moulds should not be rammed so hard as for brass. The harder metals and alloys should not be cast in closed iron moulds; but they do well in " strip " or " ingot "moulds open at top, previously dressing the moulds with whiting or plumbago; in trade foundries each one having its own preference.

Probably the amateur would find it easier to use plaster and Bath brick moulds, as with these there is only the minimum of difficulty. In the fir6t place, Bath brick is reduced to powder when perfectly dry, and after passing the powder through a 30-mesh sieve, it is mixed with fresh plaster of Paris at the rate of about two-thirds plaster and one-third Bath brick, passing the mixture through a 16-mesh sieve to insure thorough mixing. Plaster by itself is not sufficiently refractory, but when mixed in the proportions mentioned it will answer for any metal with a fusing-point no higher than brass, providing the bulk is not too large. The moulds should be made in halves, and provision must be made for pouring the metal and the escape of air, on which poinis the operator must use his judgment; but as the alloys mentioned pour "dead," there is little difficulty so long as the air has sufficient outlet. When made, the moulds should be thoroughly dried, and before pouring they should be clamped together and weighed down to prevent lifting. Damp moulds are liable to explode and to cause bad castings; therefore the matter of dryness should be closely studied. Where the castings are to be turned or otherwise machined, facing is not required, but where extra smooth castings are needed the moulds should be dusted with fine plumbago - not stove polish - before they are quite dry, and if this is brushed over with a soft brush and the moulds blown out with a pair of bellows when dry, the castings will have a fine face. Ground steatite may be used instead of plumbago, if preferred.

The metal or alloy should be melted until it is fluid; but no excess of heat should be allowed, and when it is being run into the moulds it should be poured steadily and with quickness; otherwise the moulds will run faint. Of course the crucibles should be skimmed, and no dirt or oxide allowed to get into the moulds.

An alloy that is easily melted and which has a strength approximating to that of steel, is composed of 75 per cent aluminium, and 25 per cent zinc, and this costs about 37 cents per pound for metal, and if the alloy is made for you, about 40 cents per pound. It is about half the weight of cast iron and, therefore, bulk for bulk, should cost about the same as brass at 8 1/4d per pound. This alloy is largely used for toolmaking and other trade purposes, and wears well.

A harder alloy, which will stand a good amount of strain, is made from 66.66 per cent aluminium and 33.33 per cent zinc; but it is more of the nature of cast iron. This costs 32 cents per pound for metal, or is 86 cents per pound if made up into bars. As compared with brass in bulk, it runs out at a fraction less than the preceding. The writer has seen some very decent faceplates, angle-plates, and the like, made with this metal, but the preceding formula would give better results.

A third alloy may be mentioned in regard to strength, and which will bear some amount of hammering, and is composed of 65 per cent aluminium, 30 per cent zinc, and 5 per cent copper, the cost of the metals being about 32 cents, and bulk for bulk, compares, with gunmetal at about 17 cents per pound, or in other words, castings in the alloy are about one-third cheaper than gunmetal.

Zinc broken down with copper - say, zinc 88 per cent, and copper 12 per cent - is useful for a great many purposes where strength is not required, and the alloy costs about 6 cents per pound, or, say, 8 cent6, when made up to order.

When there is no crucible furnace at hand, the alloys mentioned above should be made by a brass founder or other alloyer, and the amateur should receive them in bars or small ingqts ready for remelting. A fair price to pay for making alloys of a simple character is. roughly, a penny per pound, but large quantities would cost less. In no case will 100 pounds of mixed metals produce 100 pounds of alloy, as there are unpreventable wastes in making alloys. Loss differs somewhat with the metals used, and also with the skill of the alloyer; but in most brass foundries there is considerable skill shown in preventing undue loss. With the alloys shown above it should be possible to work out any idea in metal except where temperatures over 300° Fahr. are concerned, and inventors would with these be able to secure absolute security, as they might very well make the whole of their models.

Fusible metals of a low fusing grade could be dealt with wholly in the amateur's workshop, and in melting for the making of alloys, if care be taken to melt the most refractory metal first and then add the other metals in accordance with their fusing-points, success will, as a rule, be secured It is, however, not well to try to add zinc to copper until you have seen it done, as it splashes a great deal; nor should aluminium be added to a mixture of copper and nickel, unless there is plenty of room in the crucible, because there is a great risk of having the metal flow over into the fire and become lost. Care must also be taken in adding alkaline metals, such as sodium, potassium, and the like, to lead or tin in experimental work, as they explode violently unless they are in a very powerful carbon atmosphere - coal-gas, for instance - and as lead, tin, and other metals having a low fusing point make worse burns than iron or steel, the necessity for care is very apparent.

In conclusion it may be well to point out that when dealing with molten metal a bottle of pure raw linseed oil should always be available, as well as some white cotton thread waste or coarse lint, and if one unfortunately gets a splash of metal, the oil should be poured on freely. "Carron" oil - oil and limewater - is not so good for metal burns as pure linseed oil, according to the writer's experience. A great deal depends on condition, however, for while a heavy drinker, especially a spirit drinker, will have trouble with burns, a moderate man will find them dry up and heal without any application. The writer never worries about a few burns from molten iron or steel unless they are extensive, as they dry up very quickly; but a lead burn takes a longtime to heal. - English Mechanic.

To obtain practically pure argon the following operation is carried out: The impure argon gas is passed from the cylinder through a tube of Jena glass con-toining 45 grammes of lime ana magnesium mixture. It then passes through a second tube containing four troughs of nickel, in which are placed three or four grammes of metallic calcium in small pieces. Two mercury pumps are connected to the apparatus by a three-way cock. The first pump serves to produce an initial vacuum in the apparatus, and the second causes the circulation of the gas in the tubes, which are heated to low redness. The small quantities of nitrogen and hydrogen are retained by the calcium and the argon comes off in a practically pure state.