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messages each way over one wire, and the simple pressure of the proper key at the sending station is all that is necessary to have the corresponding character printed at the receiving station. The use of the alternating current is also a tribute to the originality and foresight of the inventor, since it lends itself very readily to the needs of telegraphic communication. The future will probably see all overhead wiring banished; and the electrical difficulties which are to arise from

THE LATE PROF. HENRY A. ROWLAND. Died in 1901.

the placing of wires underground and in cables will be more easily overcome than with a direct current.

It is hard to predict the far-reaching effect that the Rowland system will have on the telegraphic communication of the world. The messages, by automatic repetition, may be transmitted thousands of miles; and this advantage, combined with those of cheapened service and greater facility of transmission, will undoubtedly put into direct communication great world centers which have hitherto communicated with one another only by long and circuitous routes. It has also been found that the system, when once well established, has partially superseded the mails and the telephone. It will be necessary, however, to educate the public to a realization of the latent possibilities of

the telegraph. The sending or receiving of a telegram is to the average family a thing of rare occurrence; but it is to be hoped that in the future the reduction in cost, owing to the greater ease with which messages may be sent, will promote among the people a more extended use of this means of communication. It would be within the bounds of probability to say that we may some day even transmit whole letters by telegraph.

The Rowland machine, in its present commercial form, is divided into what are called the line-unit and the correspondence-units. The line-unit has for its function the operation of the line, and contains the necessary apparatus for furnishing the signaling current, impressing the signals, etc. This unit is identical in form at each end of the line. The correspondence units receive and transmit the messages; each consists of a transmitter, a receiver, and a home recorder. The transmitter is a universal typewriter keyboard; the receiver an automatic page-printing machine, which records the message in page form on a telegraph blank, ready for delivery; and the home recorder a printed tape passing along a scale before the eyes of the operator, giving a duplicate of the message sent out. There is another correspondence unit at the other station, which is the twin of the one just referred to. These two send to each other, and receive from each other, the signals going continually over the line, which are recorded exactly as a typewriter records its letters upon a page. letters upon a page. The operator, by the depression of certain keys, lines and spaces as though he were operating an ordinary typewriter. A red light takes the place of the typewriter bell, the carriage being backed and the light extinguished by the pressure of a key. When the end of a message is reached, a quickshifting device throws in a blank section of the paper before the next message is begun. In fact, the operator's knowledge of his printer's movements is so accurate that tabulation may be done. Specimens of this character of work have been transmitted over actual lines 500 miles in length. These correspondence-units are instantly and easily detachable, and if one gets out of order another can immediately be substituted for it.

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To understand the system in all its details, requires considerable study. The most that can be done in an article of so limited scope as this, is to show the bare principle upon which the machine works the application of the alternating current to the sending of signals.

The figure represents the end view of a commutator which has a brush traveling over its surface. This brush has a wire running to a source of alternating current. The segments of the commutator have relays connected to them, one of which is shown in the diagram. It will be seen that as the brush makes contact with the segment connected to the coils of any particular relay, the current can pass through the coils of that relay and back to its source. Suppose the motion of the brush and the alternations of the current to be so adjusted to each other that the current will change in direction each time the brush passes from one segment to another. This will cause each pair of coils to get a momentary flow of current in one direction or the other according to the adjustments. Suppose the relay shown receives an "impulse" of current in the direction indicated by the arrow. This current will cause magnetism to be produced in the coils, which magnetism, we shall say, throws the tongue against the contact point a.

Every revolution of the brush will have this same effect, provided the flow of current through the coils is always in the same direction. But if the particular impulse of current received by this relay is reversed in direction, the magnetic effect produced in the coils will be opposite to that in the case referred to above, and the

END VIEW OF COMMUTATOR.

Showing connections whereby circuits are opened and closed in sending messages.

tongue will be thrown against its "front stop," the contact-point b. If the mechanism shown in the diagram is placed at one end of a telegraph wire, and the impulses of alternating current supplied to it are controlled from the other end, an operator might throw the tongues to their front stops at will by reversing the proper impulses of the alternating cur

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OPERATORS TESTING ROWLAND MACHINES IN LABORATORY BEFORE SHIPMENT.

A line is built up of resistances and condensers, and over this line the machines are operated.

eleven relays and segments serve to send the 51 signals from each keyboard, whereas the illustrated case would require one relay and segment for each signal.

The multiplexing is accomplished in the following manner. The commutator that receives the impulses from the line is divided into quadrants, each containing the segments that are connected to the relays controlling one particular printer. These relays receive impulses only for the time during which the revolving brush is passing over their own segments. The keyboard of the operator who controls this printer at the sending station, is automatically unlocked at the proper time to enable him to reverse the impulses of current received by the relays controlling his printer. Thus each op

whatever with the four messages that are being sent at the same time.

The machines are very interesting from an electrical standpoint. One very striking instance of the delicacy of the regulating devices may be referred to here. The Rowland is what is called a synchronous system; that is, the moving parts at the two stations must be kept rotating at exactly the same rate of speed. This synchronism is maintained with such accuracy, by electrical means, between the two line-unit motors, each running at 1,960 revolutions per minute, that the variation in speed does not amount to 1-6 of a revolution for days at a time; this with the motors hundreds of miles apart.

The Rowland machines have been operated successfully both in this country

and in Europe. An experimental one was made the subject of exhaustive tests in Germany, France, and England; and actual telegraphic work is now being done in this country, the operation in all cases being entirely satisfactory and very gratifying in its results. An octoplex installation which has been in use in Italy for three years, afforded an excellent illustration of the advantages possessed by the Rowland system during the recent eruptions of Vesuvius. All wires in communication with Naples except that used by the Rowland apparatus were inadequate. This Rowland dispatched the correspondence easily and promptly on one wire, telegrams being transmitted at the rate of 8,000 per 24 hours.

The Rowland system has been developed without publicity or advertising, and at great expense. The invention promises to reflect great credit both upon its birthplace, the Johns Hopkins University, and the place of its development,

Baltimore. It is one of the modern achievements whose perfection is due to the labors of others besides the inventor. The present standardized machine is the result of the combined efforts of a corps of skilled engineers and a force of expert designers.

The advantages of the system as they have been proved in commercial use, may be summed up as follows:

1. It is operated by employees unskilled in the telegraphic code.

2. It records and checks errors, and enables these to be easily traced to their

source.

3. The operator attains a higher average rate of speed than the Morse opera

tor.

4. The wire is made to carry double the number of telegrams.

5. The system operates in full capacity through varying weather and at times when the Morse and others are crippled.

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He is arranging the little insect workers on the trees in the way that will best produce the strange harvest.

neys of the agile and sure-footed porters, who are forced to hurry along as fast as possible with their loads of insects on their backs, hundreds of miles, across steep and rocky mountain passes, ascending and descending precipitous places which no animal or conveyance could traverse with safety, in order to land their

upon. This insect is about the size of a mosquito. The male has a head nearly triangular and of a light orange color. The antennæ are long and composed of segments, comparatively comparatively long, light brown, and covered with grayish hair. The first pair lie far apart from the others. The four wings are long, oval, and

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