It is evident that the terminal station might em ploy a relay and sounder in place of the telephone, but the latter is naturally the most convenient, as it requires only a small battery on board the train. Again, the telephone might, with equal facility, be employed as a receiver on board the train, but it was found that the noise which always accom panies a moving train prevented a distinct under standing of the signals. A relay was, therefore, necessary, the principal requirements of which were two-fold. In the first place a very deli cate relay was required for the reception of the very weak induced currents ; and secondly, one in which the armature should not be affected even by strong jarring and vibration, such as is experienced on trains. These antagonistic elements were, however, provided for in the relay designed by Mr. Phelps, and which is represented in Fig. 33. It will be seen to consist of two steel magnets, bent as shown, with their like poles brought together and carrying an extension piece which has a V-shaped groove at the top. The other ends of the magnets carry extension pole-pieces and fine wire helices. The armature is about the same thick ness and size as a 3-cent nickel piece, but its lower edge is straight and thinned down to a knife edge, which rests in the bottom of the V-shaped groove. Thus we have friction entirely removed, while the small mass and leverage of the armature, together with the strong magnetic field in which it is placed, prevent its moving under shock or vibration. It re sponds, therefore, only to the impulses sent through the coils, and its action is very delicate in spite of its shock-resisting power.
Static Train the Phelps train telegraph is actuated by dynamic induction, the Edison-Smith system is based upon static induction, the metal roofs of the curs being so charged that they act inductively upon the telegraph wires along the line, and thus render communication possible. In the same way the wires may act upon the roofs. and a message may be received on the train.
The arrangements of the ear and the terminal station are quite simple and consist of a telephone receiver in lieu of a sounder, a Morse key, a vibrator, and an induction coil. Fig. 34 shows the operator seated at his desk, which has been installed in one of the passenger ears, and having two telephones to his ears while he receives a message.
The manner in which the messages are sent and received will appear quite plain upon reference to the diagrams. Fig. 35 and Fig. 36. The latter shows the apparatus as arranged on the car, and the former, that at the station : they do not differ materially from one another. Referring to Fig. 36, it will be seen that the metallic roof of the car is connected by wire to the switch S. When turned toward the left, the switch closes the circuit through the telephone, which is connected to the ground through the wheels of the car, and this is the position of the switch when a message is being received. When transmitting a message, however, the switch is turned to the right, which closes the circuit through the one end of the secondary of the induction coil the other end being grounded in the same way as mentioned above. The primary of the induction coil G, is joined to a Morse key it; and battery B, and interposed in the circuit is the vibrator R. When the switch S is turned, the vibrator is started, so that when the key is pressed the primary coil of G has a series of rapidly intermittent currents sent through it. The secondary of U being connected to the roof of the car, it consequently sends into the latter a series of rapidly intermittent charges of high potential. These react upon the telegraph wires and influence the condensers attached to the lines at the terminal station shown in Fig. 35. Here it will be noticed the condensers are coupled in parallel, one side of each being joined to a wire and the other to the leading-in wire. The rapidly alternating charges produced by the vibrator are received in the telephone as a series of " buzzes," or a musical note, the duration of which depends, of course, upon the length of time the key is pressed. In this way the dots and dashes are received as short and long notes.
TEMPERINGr AND HARDENINCI. The Harvey Steel Hardening Process.—In recent trials of steel armor plate by the United States Government it was found that plates, whether made of ordinary steel or of nickel steel, that had been treated by the Harvey hardening process, were superior in shot-resisting power to similar plates not so treated. (See Amon.)
The details of this process are thus described in patents granted to the inventor, Mr. H. A. Harvey, of Orange, X. J.: "The armor plate having been formed of the desired size and shape from a comparatively low steel, such as Bessemer steel or open-hearth steel, containing, say, 0.10 per cent. to 0.35 per cent. of carbon, is laid, preferably flatwise, upon a bed of finely powdered dry clay or sand, deposited upon the bottom of a fire-brick cell or compartment erected within the beating chamber of a suitable furnace. The plate may be so imbedded that its upper surfaet. is in the same plane with the upper surface of those portions of the bed of clay or sand which adjoin the sides and ends of the plate, or the plate may, if desired, be allowed to project to a greater or less distance above the surface of the clay or sand. In either case the treating compartment is then partially filled up with granular carbonaceous material, which, having been rammed down upon th^ plate, is covered with a stratum of sand, upon which there is laid a covering of heavy fire bricks. The furnace is then raised to an intense heat, which is kept up for such a period of time as may be required for the absorption by the metal adjoin ing the upper surface of the plate of, say, an additional 1 per cent. (more or less) of carbon, or, in other words, the quantity of carbon, in addition to that originally present, which may be necessary to enable the said metal to acquire the capacity of hardening to the desired degree. The temperature of the heating chamber outside of the treating compartment is brought up to a height equal to or above that required to melt cast-iron, and is kept up for greater or less length of time, according to the depth of the stratum of steel which it is intended to charge with an excess of carbon. This period, however, will, of course, vary according to the efficiency of the furnace. As a general rule, the thicker the armor plate the greater will be the permissible depth of supercarburization. A 104-in. plate and a depth of supercarburization of 3 in. are herein referred to merely for the purpose of illustration. After the conclusion of the carburizing treatment, the plate is taken out of the furnace, and without removal of the carbonaceous material from its surface, is allowed to cool down to the proper temperature for chilling. When it is seen that the supercarburized surface is so far cooled down as to have a dull cherry-red color, the carbonaceous material is quickly removed, and the plate is then chilled by being sprayed with torrents of cold fluid or by being submerged and kept in motion until cold in a large body of cooling fluid—as, for exam ple, a more or less rapidly running stream or river of fresh water, or a tidal current of salt water. The exercise of this precaution insures the subsequent uniform hardening of the subcarburized surface of the plate." Tempering steel axles.—A method of tempering steel car axles, by which it is claimed that their strength is increased and made uniform without at the same time making them brittle, and used by the Cambria Iron Co., of Johnstown, Pa., consists in heating the axle to a red heat, and plunging it into a trough filled with running cold water until the red heat visible on the surface is just about to disappear. On removing the car axle from the water the red beat returns to the surface, by conduction from the interior. The axle is then allowed to cool slowly in the air, thus partially annealing it.
Tempering steel in molten many years it has been a somewhat common practice to use baths of the easily fusible metals or alloys for quenching steel, but it has recently been attempted on a large scale at the works of the Chatillon et Commentry Company, in France. An article on the process in use at these works was published in the Iron Age of October 10, 1889.
The following table of tests of water-quenched, oil-quenched, and lead-quenched bars is given by Henry M. Howe, in his work on The Metallurgy of Steel, as results obtained by the Chatillon et Commentry Company : Tempering Wheel : see Clay-working Machines,