Largest Electric Light in the World

What is the largest size electric light made? -B. E. L.

There is an electric light in the lighthouse on St. Catherine's Point in the Isle of Wight, supposed to be the largest in the world. It is run by two dynamos, and if both work in conjunction the concentrated light is computed to be equal to 6,000,000 candle-power. The carbons have a diameter of 21⁄2 inches, which is about seven times the size of the carbons in the ordinary street arc lights. The induction arrangement of each machine. consists of 60 permanent magnets, each magnet being made of 8 steel plates. The armature is 21⁄2 feet in diameter, and composed of 5 rings with 24 bobbins in each.

Third Rail Electric Railway System What are the advantages of the third rail system of electric traction?-D. S. B.

line dye of the desired color has been dissolved. Aniline dyes of any color desired may be obtained at a drug store. Be careful not to cover the base of the lamp with this solution.

Demagnetizer

Question: I-wish to make a watch demagnetizer for use with alternating current. Will you kindly publish the formula in the next month's issue of your magazine. I want two, one to work on from 75 to 90 volts, and the other to work on 110 olts.-C. R.

Answer: No formula is required for making a watch demagnetizer. Make a wooden core of rectangular form, upon which to wind the coil. The core should taper slightly so that it can be withdrawn when the coil is wound, leaving an opening to receive the watch. The coil should be about 3 inches long, and should be wound to a depth of 1⁄2 inch with No. 28 B. & S. wire. The same coil can be used on either 75- or 110-volt circuits. If it takes too much current and heats up, reduce the current by putting a lamp in series.

THIRD RAIL ELECTRIC SHOE,

Where heavy trains are to be moved, the third rail system offers a cheaper method of transmitting the large current strength necessary to their operation. The shoes offer facilities for conveying a heavy current to the motors, because of the large area of contact. On a trolley system, the trolley wheel is destroyed very rapidly because of sparking, caused by the small area of contact between the wheel and wire. The cost of maintenance is small in a third rail system and it is much more convenient, in operation, not to have a trolley pole to watch.

To Color Incandescent Globes

How can I color incandescent lamp globes? Dip the lamps in, or paint them with, a solution of collodion, in which an ani

Case-Hardening

What is case-hardening and how is it done? —A. L. R.

The essential difference between machine steel and tool steel is the amount of carbon that they contain. If carbon be added to machine steel it will be turned into tool steel. Sometimes articles are wanted very hard on the surface to resist wear and at the same time very tough to withstand shocks. If the piece be made of tool steel in order to be hard enough, it will be too brittle, and if made of machine steel in order to be tough enough, will be too soft. To overcome this difficulty the parts are made of machine steel and then the outside is carbonized or converted into tool steel to a slight depth, and this outside coating of tool steel then hardened. The process is known as case-hardening. The method used generally consists of heating the machine steel red hot in contact with something very rich in carbon, generally ground bone. The surface of the machine steel takes up or absorbs the carbon and is converted into tool steel.

LECTRICALLY operated A labor-saving devices are at

present utilized to a very great extent in the roasting of coffee in all modern factories, the absolute cleanliness, the speed of operation and the thoroughness with which electric power does its work, all combining to make it of especial value in such installations.

Arabia, Java and Venezuela furnish a fair proportion of our coffee, but the greater part probably comes from Brazil, being imported in bags weighing 132 pounds. This is our ordinary green coffee, which is ready for roasting, if sufficiently clean. There may, however, be considerable manipulation required to prepare the green coffee for the roasters, the thorough cleaning being termed "milling," this process also making the coffee roast brighter.

The raw coffee is conveyed from a feed bin or bucket elevator, to the milling and

cleaning machine, entering a shaker-feed, which distributes it uniformly over a sieve, consisting of two sections, the first section of which sifts out the fine material and carries it to a bucket by means of a pipe, while the second section, which has larger holes, allows only the coffee to drop through and pass on, the sticks, strings, etc., being carried to another pan. The coffee which passes through the second sieve then enters the milling machine proper, which consists of revolving cylinders, between which the coffee is thoroughly scoured and brushed, the surface of the bean being smoothed and freed from all dirt and then discharged through a pipe.

An exhaust fan, placed above the machine, causes an air current through it, so that all the light waste material from the coffee is drawn up through the feed pipe and through an inclined pipe leading from the discharge hopper, slide dampers being utilized to regulate the

force of the air current, which is made sufficiently strong to lift everything but sound coffee beans, so that chaff, dust, blighted beans, etc., go up the pipes. The machines are operated by electric motors, varying in capacity from two horse power to five horse power, and have an output, in the latter case, of from thirty to forty bags per hour. Apparatus of this type also admits of adjustment and regulation, both as to the separations made and the degree of milling to which the coffee is subjected.

The next important operation is separating or grading the coffee, that is, sorting the beans into grades of uniform size and shape, and removing the round "peaberry" as a separate grade. Coffee of uniform beans always commands a better price, although this has nothing to do with its drinking qualities. Formerly a great deal of "polishing" or coloring of the green coffee was performed, but, at present, there is very little of this done since the coffee sells on its roasting value and not on its appearance in the green state. A separator is used for this work and consists of sieves for accurately grading the green coffee, a peaberry apron being sometimes used, in addition, for the perfect separation of round beans.

At the present time they are not used as much as formerly, since the sieve separators now used give improved results. In those factories, however, which are most particular about separating the peaberry perfectly, the aprons are still in use, the coffee fed to them being the peaberry grades produced by the sieves.

The green coffee is now mixed in considerable quantities, ten, twenty, or thirty bags at a time, this being simply a wholesale blending operation so as to avoid the necessity of weighing out the right proportion for each batch as it is roasted. Some manufacturers, however, hold that each grade should be roasted separately and afterward blended. Shovelling was formerly resorted to in this process, but, at present, mixers driven by electric motors are used for this purpose and are much more thorough and economical in their operation.

In handling the green coffee bucket, elevators and conveyors are employed

just as for grain, with bins constructed of galvanized iron.

The coffee is now ready for the most important operation, namely, roasting, and is transferred to the machines by bucket elevators. The correct roasting of good coffee is a delicate operation and depends upon the machinery only in part, skilled operators being essential. The coffee is carefully watched until, in the judgment of the operator, the roasting has proceeded just far enough, the color of the bean indicating when this point has been reached. The roasters, however, provide that at any period of the operation every bean is precisely like every other bean.

One of the accompanying illustrations shows a battery of eight roasters in operation in a modern factory. The roasters are built up in brick.

As soon as the roasting has proceeded far enough in the opinion of the operator, the coffee is immediately discharged into the cooler boxes, which are quickly wheeled to a cooler pipe, connected with an exhaust fan, the air of the room being thus drawn through the coffee while, at the same time, spading is resorted to, to further facilitate the cooling. This process has to be accomplished very quickly, as the coffee would otherwise become darker and darker in color, and finally take fire, causing a loss of several hundred dollars worth of beans. The cooler boxes, one of which is seen in the illustration, are arranged to tip on their trucks so as to discharge the coffee, after cooling, and are, in consequence, called "tiptop" cooler boxes.

The principle in cooling is simply to spread the hot coffee out in a thin layer on top of a sheet of perforated metal so as to quickly cool the beans by passing air through them by means of a fan. Formerly, the outlet of the fan blower was connected with the enclosed space underneath the perforated metal sheet of the cooler box, but, inasmuch as there was no outlet out of doors, the hot air rose to the top of the room. In modern practice an exhaust fan is utilized, the inlet being connected with the bottom part of the cooler and the air from the room being drawn down through the coffee and carried out of doors through a pipe.

terial such as stones and nails at the bottom of the "stoner boot." Stoning is important to render the subsequent grinding operation safe for the mill, since stones get into the coffee either by careless gathering of berries dropped on the ground or by being put in, deliberately, to add weight. It might be thought that all stones would be sifted out from the green coffee by the separating machines. This is true of those stones which are either larger or smaller than the beans, but the sieves fail to remove those which are of the same size. In roasting, however, the beans become lighter and larger, increasing the difference in specific gravity between them and these stones and, when the coffee is placed in the stoner pipe, the beans are in consequence carried up by the air current, leaving the heavier stones behind.

The handling of the coffee, after roasting, is a very different matter from handling the green coffee, since it is now easily broken. For this reason a bucket-ele

used for grinding. As mentioned before, some manufacturers prefer to mix their coffee after roasting, and in such cases the operation of blending is performed at this stage. The glazing makes dull coffee look bright and seals the beans so that they do not lose their aroma.

The finisher is merely a stout wooden drum with cast iron heads and with doors in the side for filling and emptying. It is run almost full of coffee, the finishing material being mostly water, the principal effect being produced by the friction of the coffee on itself.

In the regular glazing process, the coffee is mixed with a liquid, so as to spread it completely over every bean and then this is baked on by a hot blast of air.

The coffee is now ready for packing, although sometimes certain of the latter operations are omitted. The second illustration shows a complete coffee roasting plant, with the green coffee machinery on the right. The capacity of this plant is 200 bags per day.

HE Interior Department has been exercising, for a branch of the government, an unusual amount of business sense, if not downright spunk, in dealing, not only with other branches of the government, but with private individuals. The Secretary of the Interior is charged with the carrying out of the irrigation law and now has at his disposal over twenty-five millions of dollars for this purpose. seems determined to employ business principles in this work, without much regard to red tape methods or the protests and howls of private corporations expecting to secure large profits out of this work.

He

In most of the big projects of dam

construction in the West, large amounts of cement are necessary, and in the case of the great Roosevelt dam in the Salt River Valley in Arizona, the specifications called for 200,000 barrels. It is learned from the daily newspapers that there is a cement trust, and it is further gathered that this trust expected to coin a million or so out of the cement contract which it alone, it assumed, was competent to fill. Last winter the government advertised for bids, and the price proposed by the trust was $9 a barrel. The railroad rates were very heavy, the distance to be transported was great and the cement people controlled the situation, so they thought. By examination of one of the early reports of Arthur P. Davis, the projector of this great Salt River irrigation project and now assistant chief engineer of the Reclamation Service, the