Construction of Telegraph Wires, Tests of various insulators

[Written for THE TELEGRAPHER.]

On some Points in the Construction of Telegraph

Wires.

NO observing person, who has passed through the city of Chicago within a few months past, can fail to have noticed the new lines of the Western Union Telegraph Company which have recently been erected in many of the principal streets of that thriving western metropolis. In most American cities, at the present day, the telegraphic lines form a very prominent portion of the street scenery, but it is very seldom that they are so constructed and arranged as to present a really ornamental appearance. But in Chicago the long ranges of tall white spars and symmetrically arranged cross-arms, extending in straight lines till they are lost in the distance, unquestionably add to the appearance of the principal thoroughfares. It is worthy of note that the superior character of these lines is manifest in their working qualities as well as their outward appearance. The improved BROOKS paraffine insulator is used throughout, something like 20,000 of them having been put up in the city of, Chicago alone; they are also being largely used in other portions of the Central Division with the best results. The many improvements of this kind that are being made in the Central Division, under the vigorous and progressive administration of Gen. ANSON STAGER, will have the effect, within a few years, of making Chicago the telegraphic metropolis of the United States.

It is greatly to be regretted that the same appreciation and adoption of improvements of real and permanent value is not manifested by the officials in charge of the affairs of the Western Union east of the Alleghenies. Many new lines are being built, and many old ones rebuilt in the Eastern Division, but without the slightest improvement in principle over those of a dozen years since. It is a common remark that, during a heavy rain, a much smaller proportion of the whole number of wires is available for business than was the case a dozen years ago; and, in view of the boasted improvements continually going on, the fact has been considered somewhat difficult to account for. When the matter is carefully investigated, however, the cause of the trouble is sufficiently obvious. The time-honored glass insulator of fifteen or twenty years ago still maintains its ascendancy, in various forms, some better and some worse than the original egg form of the old "magnetic line." But the ancient "egg glass," on an iron bracket, had its good points, although it has fallen into disfavor of late years. This will be seen upon a comparison of it with the style of construction in vogue at the present time between Boston and Washington. The glass insulator now employed is substantially that first used by the United States Company, being a sort of compromise between the "egg" of the Magnetic line and the well known "petticoat" or "umbrella," so much used a few years since. It is mounted upon a wooden pin, and has a tolerably wide opening underneath. The United States Company used to turn a collar upon the pin or bracket, which nearly filled the mouth of the opening, and prevented the rain from dashing in and wetting the inner surface of the insulator. By this means they secured the best results that have yet been attained in this country by the glass insulator. One wire put up in this manner, between New York and Boston, was quite remarkable for the excellence of its insulation in wet weather.

When the Western Union Company adopted this insulator they probably found the collar upon the pin too expensive, or else they must have had some personal objection to the inventor, whosoever he may have been, for they now put them upon pins without collars, and these upon cross-arms. The result of this arrangement is that the falling rain strikes the flat upper surface of the cross-arm, and rebounds in a shower of spray a foot or two in heighth [sic] height, wetting the whole inner surface of the insulator, which is carefully arranged to facilitate this process as much as possible. In all cases where it can be done it is customary to put four wires on the same arm, from 12 to 20 inches apart, in order to facilitate the mixing of the currents from the different wires, when the insulators have become thoroughly wet. The number of poles per mile has been increased from 30 to 40, with no apparent reason except for the purpose of multiplying the number of points of leakage or escape. When we bear in mind the fact that the old egg insulators were narrow at the mouth, and that the iron hook supporting them was not largo enough to dash any great amount of water into the cavity of the insulator during a shower, it will be seen that they possessed an important advantage over the pin and cross-arm arrangement, which advantage is also shared, in a great degree, by a properly fashioned wooden bracket.

Upon the Eastern Division of the Western Union, therefore, we find that, even with the admitted imperfections of the glass insulator, great care has been taken to secure the worst possible results from its use. A careful comparative test of these with the BROOKS insulator, used in Chicago and elsewhere on the Central Division, as well as with others in general use in this country and England, gives some very suggestive and instructive results. The experiments and tests, whose results are given below, were made at the factory in Philadelphia during a heavy rain storm, on the 10th of October, 1869. The insulators were exposed in the same manner as if in actual use, in sets of five, and the deflection per insulator given below is the average of the five. The leakage from each insulator is proportionate to the number of degrees of deflection. The following is the result of the test in a tabular form: