Pressures up to 9000 pounds are obtained by the use of a heavy helical spring secured within a 4-inch wroughtiron pendulum tube. By a convenient taper-key adjustment (not shown in the cut) the pressure may be easily and quickly relieved for removal of the pendulum and brasses from the journal, without release of pressure of the spring within the tube.

The standard boxes may be replaced by the ordinary brasses used in regular railway service if desired, thus imitating the actual conditions of practice. The graduated arc on which the friction is indicated is conveniently placed above the pendulum. The standard thermometer used is graduated from 40° to 350° F. A positive automatic revolution-counter which reads up to one million is attached, enabling the experimenter to determine the comparative mileage run. The apparatus may be speeded to correspond to the rates usual for trains by suitable provision of counter-shaft and cone pulleys. This machine, including the counter-shaft, weighs 1125 pounds, and is manufactured by the Pratt & Whitney Company of Hartford, Conn. (W.)

Lubricants. Admixtures of mineral oil with animal oil lessen the liability of the latter to spontaneous combustion. A series of experiments, which were made to test the inflammability of such mixtures, by saturating balls of cotton waste with oil and measuring the increase in temperature, showed the following results: With pure lard oil the temperature increased to 428° F. in 4 hours; with pure neat'sfoot oil to 446° F. in 6 hours, and in hour more the cotton was converted into glowing coal. With a mixture of 50 per cent. of pure mineral oil and 50 per cent. of neat's-foot oil the temperature did not increase to over 214° F.

Purification of Lubricants after Use. Dissolve 2 parts by weight of potassium chromate, 2 parts of calcined soda, 24 parts potassium chloride, and 5 parts of common salt in a wooden vat. Bring into this 1000 parts of the oil to be purified previously heated to about 167° F., and after stirring thoroughly for 10 to 15 minutes let it stand quietly 8 to 10 days in a warm place. At the end of the time draw the clear oil off by means of a cock on the vat.

Used lubricants can also be purified in the following manner: Heat 1000 parts by weight of the oil to be purified to about 167° F. and add with constant stirring a mixture of 10 parts by weight of concentrated sulphuric acid and the same quantity of 96 per cent. alcohol. After 24 to 48 hours rest the oil is drawn off from the sediment and, to remove all traces of sulphuric acid, washed with boiling water.

New Receipts for Blacking. No. 1. Melt 90 parts by weight of beeswax, 30 of spermaceti, 350 of oil of turpentine, and 20 of asphaltum lacquer, and mix with 10 parts by weight of borax 20 of lampblack, 10 of Berlin blue, and 5 of nitro-benzole.

No. 2. Dissolve 150 parts of wax and 15 of tallow in a boiling mixture of 200 parts of linseed oil, 20 of litharge, and 100 of molasses. Heat to 230° to 248° F. with an addition of 100 parts of lampblack. When cold dilute with 280 parts of linseed oil and mix with a solution of 5 parts of gum-lac and 2 of aniline violet in 25 of alcohol.

No. 3. Mix intimately 6 parts of fine bone-black, 28 of syrup, 4 of sugar, 3 of train oil, and 1 of sulphuric acid,

and allow the mixture to stand 8 hours. Then add with constant stirring 4 parts of decoction of tan, 18 of boneblack, and 3 of sulphuric acid, and pour into boxes.

point," consists simply of a grain of iridium soldered on the point of the pen, which is afterwards sawed in two to make the two nibs and ground into proper shape.

For preparing larger pieces of irid

METAL INDUSTRY.

Hardening Composition for Steel. To the ordinary hardening composition consisting of 4 quarts of fish oil, 2 pounds of beef suet, and pound of wax, it is recommended to add 1 pound of rosin. Another composition consists of 95 quarts of spermaceti oil, 20 pounds of melted tallow, 44 quarts of neat'sfoot oil, 1 pound of pitch, and 3 pounds of rosin. After melting the last two together the other ingredients are added and the mass is heated in an iron vessel until all moisture is driven out and the heated mass ignites from a burning chip of wood held over it; the flame is at once extinguished by a closefitting lid. In using either of the methods for saw blades they are first heated in a suitable furnace and then placed vertically, teeth upward, in troughs filled with the mixture. After sufficient cooling they are taken out and wiped with a piece of leather so that only a slight film of fat remains. They are then placed flat over a coal fire until the coating of fat ignites, which may burn as freely as required for great hardness. Screws or other articles which are to receive a less degree of hardness are dipped into the hot mixture and brought to a red heat. Iridium, its Preparation and Use. With the exception of alloying with platinum the principal use of iridium up to the present time has been for pointing gold pens. The iridosmine, called by the manufacturers "diamond

For making points for the Mackinnon pen, the fused metal is poured between two iron plates which are kept apart a proper distance so as to make a sheet of iridium of the desired thickness. To obtain very compact castings, the plates are brought suddenly together, on the plan of a closed ingot with a hinge, so that as the metal cools it is subjected to great pressure. The sheets required for the Mackinnon pen are about 31⁄2 inch in thickness, and are cut up into small irregular pieces, which are soldered on a strip of bronze and ground down to a flat surface upon a copper lap. Corundum or diamond dust mixed with oil is applied to the flat surface of the lap by means of a flat steel instrument, upon which pressure is applied in order to force the corundum or diamond dust into the copper, thereby making a cutting surface. The lap makes about 800 to 1000 revolutions per minute. After the pieces are ground to a surface they are first countersunk by means of a diamond drill making about 900 revolutions per minute. After countersinking the iridium is finally pierced by means of a copper wire held by a suitable drilling apparatus, which makes about 3500 revolutions per minute. Some corundum or diamond dust and oil are put in the countersunk opening in the iridium and then it is held up against the piece of revolving copper.

The holes having been drilled, the

The most difficult objects are obtained with the aid of open or closed iron or steel moulds, which are previously heated to prevent too rapid cooling. By fusing the phosphor-iridium several times, a part of the phosphorus evaporates, and the melting point becomes higher. If heating is continued too long, the metal does not fuse, and phosphorus must be added in order to give it its former properties. The process of removing the phosphorus after casting is as follows: The metal to be dephosphorized is placed upon a perfo

Phosphor-iridium, as this metal may be called, possesses some very remarkable properties. It is as hard, if not harder, than iridosmine from which it is prepared. It is somewhat lighter, owing to its percentage of phosphorus and increase of volume. It is homogeneous and easy to polish, and forms some alloys impossible to prepare in any other manner. It combines with small quantities of silver and forms with it the most flexible and resisting alloy of silver. With gold or tin no alloy has thus far been obtained. Added in small quantities to copper it furnishes a metal possessing very small resistance to friction, and especially adapted for articles subjected to great pressure. This alloy seems to possess more than any other metal the power of retaining lubricants. With iron, nickel, cobalt, and platinum, phosphor-iridium forms combinations in all proportions, which are of great importance. With iron an alloy is obtained which retains the properties of phosphor-iridium, although its hardness decreases with a larger addition of iron. The alloy is slightly magnetic, and is not attacked by acids and alkalies, and the best file produces no effect upon it even if it contains as much as 50 per cent. of iron. With more than 50 per cent. of iron the power of resistance decreases gradually and the nature of the metal approaches that of iron.

In casting phosphor-iridium it is observed that the mould fills up better after a second and third fusion.

tom of the crucible and surrounded with powdered lime, and then heated for some time to a red heat. The phosphorus combines with the lime and forms a green slag which collects upon the bottom of the crucible. After some time the crucible is taken from the fire and the metal, after cooling, is once more treated in the same manner in another crucible. The temperature is gradually raised until the metal is completely dephosphorized.

Cowles' Electric Furnace. The Cowles Brothers, of Cleveland, Ohio, have lately invented a process of reduc ing the refracting ores of many metals by electrical means, which promises to become very important in the arts. They construct a rectangular box of fire-resisting material, lined with a mixture of fine charcoal and lime. It has a removable cover, which is perforated with openings to allow the escape of gases evolved. In the sides of this furnace the electrodes-2 plates of gas carbon-are let in, by means of which the current of a powerful dynamo-electric machine is introduced. The charge consists of a mixture of the coarsely crushed ore and coke fragments. The essential feature of the process consists, therefore, in employing in the furnace a substance like carbon whose high resistance to the passage of the current causes the production of a prodigiously high temperature, and which at the same time is capable of exercising a powerful reducing action on the ore. With such an arrangement of apparatus, and by the use of a powerful electric current, the inventors have succeeded in reducing aluminium from corundum, boron from boracic acid,

Refining Nickel (Fleitmann's Process.) Dr. Fleitmann, of Iserlohn, has devised a very simple and successful process of refining and toughening nickel, which is now very largely used. It produces a very homogeneous metal from which castings may be made with much less liability to the presence of blow-holes than with other methods. Fleitmann's procedure consists in adding to the molten charge, in the pot, when ready to pour, a very small quantity of magnesium. The magnesium is added in small quantities at a time and stirred into the charge. About one ounce of magnesium is found to be sufficient for purifying 60 pounds of nickel. The theory of the operation is that the magnesium reduces the occluded carbonic oxide, uniting with its oxygen to form magnesia, while carbon is separated in the form of graphite. The nickel refined by this method is said to become remarkably tough and malleable, and may be rolled into sheets and drawn into wire. Cast plates (intended for anodes in nickelplating), after reheating, can be readily rolled down to the required thickness, which greatly improves them for .plating purposes, as they dissolve with greater uniformity in the platingbath. Nickel so heated may be rolled into sheets as thin as paper, and has been successfully welded upon iron and steel plates. (Ŵ.)

Wrought-iron (or Mitis) Castings. Ostberg, a Swedish inventor, has lately devised an ingenious process of making castings (clean and sharp) of wroughtiron, by taking advantage of the observation which he made that the addition of an extremely small quantity of aluminium to wrought-iron, kept at a white heat in a crucible, forms a combination which has a much lower point of fusion than wrought-iron.

When wrought-iron is heated in crucibles until it has become pasty, the aluminium in the form of an alloy of iron and aluminium is introduced.

Mechanically Hardened Steel. A bar of steel heated to a cherry-red is placed in a space enclosing it accurately and subjected to an enormous pressure by means of a hydraulic press. It is then allowed to cool under pressure, when it will be found that the steel has acquired a high degree of hardness and is very much inclined to become strongly magnetic. Magnets prepared according to this method possess an extraordinary power of resistance, and are already used for telephones. Steel hardened by pressure is also very suitable for edge tools, and finally the degree of hardness can be modified at pleasure by regulating the pressure.

New Solder for Metal, Glass, and Porcelain. A soft alloy which adheres to metal, glass, and porcelain, and can be used in the same manner as soft solder, is prepared from finely-powdered copper-copper dust-which is obtained by shaking a solution of blue vitriol with granulated tin. The solution becomes considerably heated, and a fine brown powder is precipitated. Of this copper dust, 20, 30, or 36 parts by weight, according to the desired hardness of the solder, are mixed in a cast-iron or porcelain mortar with sulphuric acid of 1.85 specific gravity to the consistency of paste, and 70 parts of mercury added with constant stirring.

When the amalgam is thoroughly mixed, it is carefully washed with water to remove all traces of acid, and then cooled off. In 10 to 12 hours the mass becomes harder than tin. When the solder is to be used, it is heated to 1300° F., and can be kneaded like wax in an iron mortar. In this plastic condition it is applied to the surfaces to be joined and the latter pressed together. After cooling, the solder is hard and adheres very firmly.

Oxidized Silver. Solution of penta