Publication: Report on Telegraphs and Apparatus
Washington, DC, United States
7. Supports, Insulators, And Conductors.—In this department of telegraphy, there is also but little improvement since the latest reports. Iron posts, constructed in vertical halves, which were bolted together, were shown both by the Messrs. Siemens and by the French administration. There were no specimens, so far as I could ascertain, of wooden poles prepared with creosote or sulphate of copper, which are used to some extent on the continental Hues. The porcelain insulators, common on the continent, were shown in all the departments. Siemens also displayed his own pattern, the Varley, used principally in England, and the Brooks paraffine from Philadelphia, which has obtained a foothold in several foreign countries.
11. Insulators.—The insulators employed are of porcelain, attached to the post by means of an iron strap, which encircles the insulator, the strap in turn being fastened securely to the post by screw-bolts. There are two sizes of this insulator in use. One of large dimensions for the heavy wire, and the other of smaller size for the lighter wires. The wire is suspended in an iron hook. In the larger insulator, this hook is covered with hard rubber; with both sizes, the strap, screw-bolts, and hook are galvanized. The cost of the large insulator is two francs and seventeen centimes each, that of the smaller size sixty-five centimes.
27. MODERN LINE CONSTRUCTION.—The number of posts per mile usually employed in this country is double the number used in Europe. The greatest number used in England is twenty for ten-or more wires. In France it is about sixteen; yet their lines are very substantially built.
If a No. 8 wire is stretched one span at a time, and pulled up to the full strength of two men, and the poles are thirty or more to the mile, such Hues will be so tight as to break from contraction in cold weather, provided the line has been strung during the warmer mouths. On curves and angles this contraction forces the posts out of line; but if the posts are but twenty or less to the mile, two men cannot pull up the span so taut as not to leave sufficient curve or slack in the wire to counteract the strain which it will probably suffer from contraction during the cold season. The breaking-strain of a No. 8 wire is from twelve hundred to eighteen hundred pounds, according to its quality. To bring up the span to within twenty inches of being straight, requires a tension of about four hundred and twenty pounds where the poles are stationed twenty to the mile. The same force will bring up the span to within twenty-four inches of being straight where sixteen poles to the mile are employed. Such a strain will split or detach any ordinary wood-bracket or pin, when the wire is strung one span at a time, and tied or fastened to the common glass insulators. The support of the French insulator is a wrought-iron bracket, weighing three and a half pounds, and has sufficient strength to sustain a tension of one thousand pounds without bending or breaking. This system of a reduced number of posts is not practicable, with the common glass insulators of our country. They are of too frail a nature. As used with thirty to forty poles to the mile, a large percentage of them are broken in suspending the wires, so much so that not unfreqnently as much as 30 per cent, goes to waste in this manner.
It has been objected to the system of a reduced number of posts, that the wires are more liable to be broken by sleet, but this is by no means a necessary consequence. A No. 8 or No. 9 wire of good quality will sustain the necessary tension, say three hundred and fifty to four hundred and fifty pounds, and an additional strain of one thousand pounds without breaking, a strain far greater than that which the sleet is able to bring to bear upon it; but if fifty posts are used to the mile, with wires pulled tight, the sleet will be able to break every span. With sixty posts to the mile, to avoid this very difficulty over the Alleghanies, the writer has seen the wires entirely prostrated by sleet, owing to the tight stretching of the wires, it has likewise been urged that the wires are more liable to be crossed and twisted by high winds, but with a secure fastening at the insulators, such a result does not follow. The weight of the wires keeps them at their proper distance apart; and when moved by the wind they "swing and keep time together."
The illustration (Fig. 2) herewith appended, shows the method adopted by the French in supporting their wires. Two poles are set about seven feet apart, and in a line at right angles to the direction of the wires. These posts are firmly secured to each other by an iron bar, one and a quarter inches in diameter, fastened with screw-nuts. Upon the side bearing against the strain of the wires is placed a third post, in the form of a brace. This brace is omitted where the wires are on the straight line, but is erected when this is otherwise. This, arrangement forms an immovable support, capable of safely carrying twenty or more wires.
The illustration (Fig. 3) shows the Austrian method of accomplishing the same purpose. By placing the cross-arms upon each side, and attaching them to the posts with screw-bolts, a structure of great strength is obtained, and at a less cost than upon the French system.
28. INSULATORS.—The exhibit of insulators in the Prussian department of the Vienna Exhibition, comprising more than twenty different styles, include in the list the earlier kinds, as well as those at the present time in use by that government. That employed at present was first designed by Colonel Chauvin, formerly director of the Prussian telegraphs. It has a double shed or drip, of greater height than is usually employed, and is placed in an iron bracket of great strength, weighing about three and a half pounds, so formed as to prevent the under surface of the instrument from being wetted by dashing drops of rain.
The first insulators employed on the continent were of glass, and not unlike those in use at the present day in this country. The observation was, however, soon made that the instruments would afford better results when constructed of porcelain. The choice of this material for the above purpose, however, involved the necessity of constant care in selecting the good from among the defective, inasmuch as its quality varies greatly even with pieces from the same burning. The defective pieces are porous, not having received sufficient fusion in the kiln, and consequently are readily permeable to moisture. To detect these defective pieces, for rejection, requires the use of a static galvanometers. When these precautions are observed, a much better material for insulators than ordinary glass is obtained; besides which, it possesses greater strength, and is susceptible of being molded into forms more suited to the purposes of practice than is glass.
29. The form of instrument known as the Prussian insulator is manufactured largely in France and Belgium. It is used in Germany, France, Italy, Norway, Sweden, and Russia. Those used in Germany are manufactured in Berlin. The French manufacturers make these insulators of the same material as is employed in the manufacture of the French china ware. With this single exception, material quite as good is made in this country at the Trenton, N. J., potteries as is made in Europe; but porcelain has never been used for this purpose with us, and consequently the method of selecting the good from the bad by the use of a static galvanometers is unknown. As made in France or Prussia, the cost of the Prussian insulator and its iron bracket is about fifty cents each.
The firm of Siemens Brothers, of England, exhibit all the varieties of insulators manufactured in their works, from the early history of the telegraph. Their exhibit includes all or nearly all the forms of this instrument used in England, or manufactured therefor export. Among the latter is the Brooks insulator, the invention of the writer, very similar to those made in the United States.
30. While in Europe, in the year 1867, the writer procured sets of insulators of the following nationalities: Wurtemberg, Italy, Sweden, Denmark, Russia, Prussia, France, Belgium, Switzerland, Austria, and England. Of the last-named nationality there were three standard kinds, viz: the United Kingdom's, the British and Irish Magnetic Telegraph Company's, and Varley's Double Inverts. These instruments were procured for the purpose of galvanometric measurement and comparison with those of this country, including the form manufactured by the writer. Of these several instruments one hundred and nine separate tests, during the occurrence of rain, have been made and recorded within the past six years, the results of the same having been quite uniform. The following is a summary of these results: The instruments of the French-Prussian pattern gave the best results, exceeding the best of the English insulators in the proportion of four and a half to one; and exceeding the poorest English in the proportion of five to one. Of all the European instruments the English proved to be the poorest, their performance averaging within a fraction of that of the common glass insulators in use in this country. Had the average of two hundred measurements been taken, so as to include the lighter rains, which did not seriously affect the other insulators, the average performance of the English insulators would have been much lower, even below the American glass insulator, inasmuch as a moderate rain produces a much more serious effect upon them.
31. There is no function in its operation which so seriously affects the economy and efficiency of the telegraph as its insulation. It is by no means uncommon, upon a wet day, for a person to leave a dispatch at the telegraph-office in Philadelphia, directed to New York, and thereupon to take the cars and arrive before the dispatch.
To transact the business between New York and Philadelphia, there are, probably, as many as forty wires. On a fair day, the entire business can be executed upon four wires, with the use of the printing-instruments, with an average delay of less than five minutes to each message. But as a result of their very defective insulation, where they have been exposed to the effects of a few hours' rain, the whole of the wires, worked to their utmost capacity, are insufficient to save the business from hours of delay.
The French, in virtue of the better system of insulation which they have adopted, are able to effect far more upon one wire between Marseilles and Paris, or Lyons and Paris, or Havre and Paris, than the English between London and Liverpool. In equally wet weather, the superiority of the French over the English practice, measured by the amount of work which each is able to perform, will be in the proportion of three to one, at least, and, more probably, in the proportion of five to one. On all the leading routes in France, the Hughes printer is worked, in the rain, at full speed. On corresponding routes in England, it is only possible to work the Morse instrument, and that at a very reduced rate of speed, in spite of the fact that the English have the advantage of larger wires, greater conductivity, and shorter circuit-distances.
32. The French work two wires in all kinds of weather, direct from Paris to Berlin, with the use of the Hughes printer; but are unable to work direct to Vienna, because of the inferior character of the insulation of the Swiss wires, upon which a common glass insulator is in use. The Swiss authorities admit the imperfection of their insulation, and are at present engaged in remedying the evil by introducing the Prussian insulator, as manufactured at the Belgium potteries. The sample specimens of this insulator, shown to the writer in Berne, were somewhat inferior to those manufactured in Prussia.
They are unable to work from Paris to London with the Hughes instrument, on account of the defective character of the English insulation, but can work from Paris to the English side of the channel, where re-transmission is made.
33. In his Handbook of Practical Telegraphy, Mr. Culley gives, as the insulation per mile of a No. 4 wire, in rain, between Dublin and Belfast, while "working well," 91,900 units, and that of a No. 8 wire in the same circuit and under the same circumstances, as 112,000 units. Lines of any length, say, two hundred miles, cannot be worked with such an escape in this country with our American system of closed circuits; yet there are wires in use by our railroad companies of that length, with three times the resistance of a No. 8 wire, added in the form of relays» working well in rain.
The English endeavor to overcome the effects of bad insulation by the use of larger wires, upon the following principle: If a wire of a given size or weight per foot works up to a certain capacity one hundred miles in the rain, then a wire of twice the size and weight can be worked two hundred miles to the same capacity in rain, making allowance for the increased number of insulators. If the same number of posts were used on the larger wire, that is, half the number per mile, then the larger wire would have exactly equal capacity with the smaller one of half the length. To mitigate the effects of their bad insulation, the English have ground-wires attached to their posts to carry the leaking current to the earth, instead of into the other wires or each other. They also have » separate battery for each wire. This necessitates the employment of forty thousand cells of battery at the central station in London, a sufficient number, used as main batteries, to work all the lines of telegraph in Europe, provided the same were properly insulated.
Theoretically considered, there are fewer cross-currents and disturbances in rain, when working with a separate battery for each wire, than when a number are worked from the same battery, but when the wires are as well insulated as those of the French, this difference is practically inappreciable.
The English, in their telegraph practice, have labored under the disadvantages of bad insulation from the beginning. On this account, the old needle-system was retained in use by them for twenty years, simply because the condition of their wires would admit of no other. Five per cent. of the current leaving the battery will operate the needles at the other terminals; but the speed attained upon the needle-system is no more than half that of the Morse, while the liability to error is twice as great. The condition of the wires in England at this day is improved to the extent of admitting the Morse system of open circuits, but to operate them upon the American system, which is far more economical and convenient, would be impracticable.
34. The extent to which the Hughes printing instrument is used in England and in France, affords a good standard of comparison by which we may judge of the comparative excellence of the insulation of the wires in the two countries.
In the London central station there are employed—
Hughes printers . 12
Automatic . 40
Ink-recording Morse . 240
Duplex . 20
Single needle .130
Sounders . 12
Bright's bells . 6
Total instruments . 460
In the central station at Paris, there are employed—
Hughes printers . 70
Morse ink-recorders . 30
Total instruments . 100
The average daily business of Paris proper, not counting repeated messages, but only those originating in Paris to go to other points, and those delivered in that city, amounts to as much as 12,000 dispatches; at times it has reached as high as 15,000.
The average daily business of London, as the writer has been informed, is 15,000 dispatches, but the repeated and local dispatches of the London central station reach upon an average 15,000 dispatches. The statistics of this kind of business at Paris, the writer was unable to obtain, but it is trifling when compared with that of London, since the system of transmission with pneumatic tubes is employed in Paris to a much larger extent than in London.
If the insulation is inferior, the needle system can be operated with the least difficulty; next in order is the open-circuit Morse system to which reference has been made before; while to be able to use the Hughes printer necessitates comparatively perfect insulation. For this reason the Hughes instrument is little used in our own country.
In clear weather, the condition of the wires permits of its employment with all of its advantages, but when the wires are under the effects of rain, these instruments must be placed aside and the Morse substituted, and the dispatches are transmitted at a very reduced rate of speed.
To have two sets of instruments, the one for fair and the other for foul weather, is neither advisable nor economical; so that in this country as well as in England the printing instruments are used but to a very limited extent, and even this limited use is confined to the shortest circuits and the largest wires.
35. UNDERGROUND WIRES IN CITIES.—The wires are run under ground in the cities of Berlin, Dresden, Breslau, Dantzig, Stettin, Hamburg, Bremen, Cologne, Frankfort on the Main, Mayence, Carlsruhe, and other large cities and towns of Germany, and in Geneva, Lausanne, Berne, Neufchatel, Zurich, Winterthur, Schaffhausen, Saint Galle, and Lugano, in Switzerland. In nearly all the cities of Europe neither posts nor wires are visible, but the system of underground cables is adopted instead. These cables contain from five to seven conductors each, insulated with gutta-percha, and the whole protected with an armor of iron wires. This system has shown itself in practice to be both economical and reliable. There are now in Paris working lines that have been buried for twenty years, and which have been the cause of little or no expense except their first cost. It is especially worthy of note in this particular that during the reign of the commune, when almost every institution of public utility was destroyed» not an underground wire was disturbed.
There are, probably, five times as many wires in our cities as in European cities of equal size and importance, a condition which is attributable entirely to competition between rival companies, and the consequent multiplication of needless branch offices. One of the most obvious results of this condition of things is that our finest avenues are obstructed, and their appearance marred by unsightly posts and wires. In no part of Europe, not even in the by-ways of the country, do we see such ill-prepared and ill-shaped posts, standing so persistently out of perpendicular, as may be seen in any of our finest thoroughfares. Expensive flagstones and pavements are broken up and injured to make way for these unsightly fixtures, from which, from present indications, there seems to be no relief.
Another disadvantage of this system resides in the fact that the posts so exposed are frequently destroyed by fires, &c., and the working of the wires interrupted when they are most urgently needed.
Wires on mountains are often broken by accumulations of ice and sleet. Our wires to the Pacific have been interrupted from this cause for weeks. In Switzerland the passes of Saint Gothard, the Simplon, and others are crossed by cables laid on the ground, and telegraphic communication effectually preserved by that means. The French accomplish the same object by the use of an iron wire seven millimeters in diameter. This wire is of such size and strength as to withstand any accumulation of ice and sleet.