Part 8

Hidden beneath our highways lie gas pipes, water pipes, railway tracks, Edison tubes, cement-lined iron subway ducts, and lead-covered cables. These are the electrodes. In contact with these conductors is the soil, containing an electrolyzable salt--chloride, nitrate or sulphate of ammonia, potash, soda, or magnesia, generally. In the presence of moisture this soil becomes an electrolyte, or salt solution. In the absence of electricity no appreciable damage occurs; but the passage of an electric current, no matter how small, from one pipe to another is sure, sooner or later, to leave its traces upon the positive conductor in the form of a decay other than mere oxidation. It is to this decay that has been given the name of _electrolysis_; so that when this heading appears in the daily press or in technical journals one may interpret the term popularly as “the electrolytic corrosion of metals buried in the soil.”

To produce electrolytic disintegration of pipes, etc., on a scale grand enough to cause apprehension, a bountiful source of electricity is essential. Unfortunately, this condition is not lacking to-day in any town in which the usual overhead trolley electric railway is in operation. This system of electric propulsion is based upon the use of a “ground return”--that is to say, the electricity passes out from the power house to the bare trolley wire, thence to the pole on the roof of the car, thence through the motors to the wheels, whence it is expected to return to the power house, _via_ the rails.

As a matter of fact, however, the released electricity by no means confines itself to the rails and the copper return feeders--legitimate paths provided for it. It avails itself, on the other hand, of what may be termed, for brevity’s sake, the illegitimate return--comprising all underground electrical conductors except the rails and return feeders, and including subterranean water-courses, sewers, and metallic earth veins.

In the light of our experience of the last eight years, it is easy to identify as electrolysis the effects shown in the accompanying cuts of buried metals that have been actually subjected to a flow of electricity. It is not to be inferred that the destructive action here depicted is universal throughout our towns, but, rather, that the damage occurs in spots, its rate of progress being dependent upon the amount of current and the duration of the flow. Dry, sandy soils tend to keep down the flow of current by interposing a high resistance, so that in such localities electrolytic effects are not as pronounced as in wet, loamy soils. In the same way, the character of the pipe surface--or coating, if there be any--acts as a partial barrier to check the passage of electricity.

Until recently it was generally supposed that cast iron was not attacked--at least not rapidly enough to cause alarm. In Brooklyn the water mains, of very hard, dense, even-grained cast iron, containing alloyed rather than combined carbon, have not been appreciably corroded. At Dayton, Ohio, on the other hand, seventy-seven thousand dollars’ worth of damage has already resulted. One peculiarity of electrolyzed cast iron is that the original shape is usually retained, the iron being eaten away and leaving a punky formation of pure or nearly pure graphite. In such a case a superficial examination detects nothing wrong, and it requires a mechanical scraping to show that the strength is not there. For this reason good photographs of cast-iron electrolysis are somewhat hard to obtain.

The reason for the comparative immunity of cast iron is not as yet definitely understood. It certainly does not lie particularly in the asphaltic varnish usually applied, for this varnish affords little or no protection when used upon wrought iron or other metals. Nor can it be accounted for by the composition of cast iron itself, inasmuch as a fractured or brightly scraped surface of cast iron shows approximately the same symptoms as other metals when acted upon by a given current for a given time. Whether the iron oxide is the saving feature, or whether the “skin” due to the process of casting acts as an insulator, is not yet settled.

When the trouble first appeared in Boston, in 1891, its cause was promptly identified. The electric-railway construction of those days was so crude, however, that many well-informed electricians fell into the error of assuming that heavier rails, more and larger return feeders, and better bonding (i. e., wire connections from rail to rail, around the joints, designed to decrease the resistance) would prove a panacea for all electrolytic ills. Indeed, this view is still held by a surprisingly large number of men versed in matters electrical.

I am of the opinion that it is impossible, from a financial standpoint, to provide so satisfactory a legitimate return that considerable electricity will not seek a path through pipes, cable covers, etc.; for, in order to confine the electric current to the rails, the resistance of the earth and its contained pipes would have to be infinitely great, and this condition can be realized only by making the resistance of the rail infinitely small as compared with that of the earth. The cost of arriving at this condition is prohibitive, and the improved track return is, and always must be, a palliative merely, not a cure.

Assuming, then, that under the most favorable character of electric-railway construction some of the current may be expected to stray from the straight and narrow path, it behooves us to consider how it may best be cared for in order that it may not cause electrolysis. Since corrosion of this nature occurs only at those points where electricity _leaves_ the metal, one might suppose that the attachment of a conducting wire to the affected part would result in the harmless carrying away of the current. In isolated cases, in small towns, such a plan might accomplish the desired result. It is open to the objection, however, that it in a measure legalizes the conveyance of electricity on conductors other than those designed for the purpose. In larger towns, with more than one power house and with car lines radiating from and circumscribing the business center, the attachment of conducting wires entails a ceaseless disturbance of the electrical equilibrium, curing the evil in spots and developing new danger points. Furthermore, these connections tend to decrease the resistance of the total illegitimate return, thereby tempting a greater flow of electricity along other paths than the rails and track feeders. It has been generally believed that this increased current would develop electrolysis at the ends of the pipes, due to the jumping of the electricity around the presumably high resistance of the joints; and, indeed, many samples of such corrosion are in existence. I have found, however, that it is possible to calk a bell-and-spigot joint in cast-iron pipe in such a manner that the resistance is practically _nil_; and as for wrought iron or steel, the joint resistance may be made as low as we please by fitting the surfaces so carefully that white-leading is unnecessary.

Arguing from the fact that the negative electrode is not attacked, it has been suggested to employ an auxiliary dynamo and a special system of wiring, in order to maintain the pipes, etc., at all times and at all points, negative to the rails. Could this ideal condition be realized, the rails alone would suffer. We can not hope, however, to thus easily solve the problem in towns where the distribution of buried conductors is at all complex.

It has been suggested, also, to discourage the flow of electricity along pipes and cable covers by inserting insulating sections of wood or terra cotta. This plan has never been tried on a scale large enough to afford a suitable demonstration of its utility. While it might reasonably be tried on new construction, its application to old work is almost prohibited by the attendant expense.

Attacking the problem from a directly opposite standpoint, there seems to be a chance of successfully invoking the aid of some purely chemical method of rendering lead and iron innocuous, electrolytically speaking. If we can obtain an insulating oxide, lacquer, or varnish that will retain its high-resistance properties during the ordinary lifetime of the buried metal, it will be possible to effectually protect pipes and cable coverings by coating them prior to burial. Or, if we can stumble upon an electrolysis-proof alloy, formed by the addition of a few per cent of some foreign metal to the pipe material during manufacture, the buried conductor will need no protection whatever.

But, supposing that we discover this lacquer or this alloy and by such means guard against damage to all new construction, how are we to care for the metals already buried? We can not dig them all up and paint them, neither can we attempt to replace them by the new alloy. I do not see that the state of the art to-day presents any solution of the difficulty, other than the banishment of the single trolley system. None of the electrical remedies (so called) offers more than partial and temporary relief, and the chemical field is just beginning to be explored.

Permit me to state most emphatically that this is not intended as an argument in favor of the abolishment of single trolley systems. Our civilization owes more to them than could be rehearsed in catalogue form within the limits of one issue of this magazine. We have nothing at present that can be employed as a satisfactory substitute for the ordinary electric railway. The underground trolley is a safe substitute, but the great expense of installation renders it available for very few localities. The overhead trolley, with two wires and no ground return, is cumbersome, vexatious, and unsightly. The storage battery is more or less experimental in its nature. The electro-magnetic contact systems, with plates set in the pavement at stated intervals, make no pretense of avoiding electrolytic troubles. The compressed-air motor has yet to receive popular approval.

There seems to be a mistaken impression abroad that the railway companies are indifferent to this subject. So far as my experience and information go, this is not the case. They are only too anxious to find a remedy--not, as some electricians have stated, to save their coal-pile, for energy is wasted in forcing the electricity back to the power house, no matter what the path, but because they fear that at some future date the taxpayer, the corporation, and the municipality will band together, present overwhelming bills for damages, and sweep the trolleys off the face of the earth. The instinct of self-preservation, if nothing else, demands that the electric-railway companies should put forth every endeavor to solve the electrolysis problem.

And yet, conservative judgment requires that the railway companies should not take the initiative. It is one of boyhood’s maxims not to shoot arrows at a hornet’s nest unless one has mud handy to apply to the subsequently afflicted part. Thus it happens that the railway company remains apparently inactive, bearing the burden of public condemnation, while we, whose lethargy is responsible for failing pipes, read electrolysis articles in the daily press and wonder how soon the impending catastrophe is likely to occur.

This condition of affairs is deplorable; for, while we may not care how extensively or how frequently the city authorities or the private corporations are obliged to renew their underground metals, we are at least vitally concerned as to whether the stray electricity is endangering our steel office buildings, our bridges, our water supply, our immunity from conflagrations, and the safety of the hundred and one appliances that go to make up our modern civilization.

Are the Brooklyn Bridge anchor plates going to pieces, or are they not? Are the elevated railroad structures about to fall apart, or are they not? The consulting electrical engineer says “Yes,” the railway man says “No.” The municipal authorities say nothing. “When doctors disagree----”

I deem it doubly unfortunate that so much valuable brain energy has been inefficiently expended in the discussion of electrolysis. Each writer has viewed it from his own standpoint. Electrical literature has acquired in this way a series of views, interesting and instructive, but also bewildering. There is no composite view, such as might be obtained from the report of a commission composed of a technical representative of each of the interests affected. So far as I am able to learn, such a commission has never existed.

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A curious coincidence of superstitions, illustrating anew how all men are kin, is exemplified in the native belief, mentioned in Mrs. R. Langloh Perkins’s book of More Australian Legendary Tales, that any child who touches one of the brilliant fungi growing on dead trees--which are called “devil’s bread”--will be spirited away by ghosts. An English reviewer of the book remembers having been dragged away from a fungus of this kind for the same reason. In the north of England children used to be told that, if they touched the dangerous growths, a fungus of the same kind would grow from the tip of every finger.

WINTER BIRDS IN A CITY PARK.

BY JAMES B. CARRINGTON.

Most of us are so used to thinking of birds, if we notice them at all, as belonging to spring and summer that we easily fail to see or hear the comparatively few feathered winter visitors. Among these, however, are some of the most attractive and amusing of birds, and to hear their cheery notes and to watch their busy hunt for food on a cold winter day adds a very considerable pleasure to a walk in a city park or the near-by woods. In New York city bird lovers have learned that Central Park is one of the very best places in which to watch birds both summer and winter. There is room enough there and the conditions are varied enough to offer congenial dwelling places for nearly all of the better-known birds. In the spring and fall the beautiful and tiny migrating wood warblers find the park a good feeding ground, and a safe place wherein to linger for a brief time on their journeys north and south.

With the approach of winter the innumerable fat and saucy robins that have hunted angleworms and strutted about the lawns of the park since early spring disappear, except for an occasional hardy fellow who perhaps prefers the dangers of a northern winter to those of the long journey southward. The wood- and the hermit-thrush; the veery, or Wilson’s thrush; the yellow warbler, so abundant and so musical; the perky little redstart, whose song of “Sweet, sweet, sweeter” closely resembles the yellow warbler’s; the somber-colored blackbirds; the Baltimore and the orchard oriole; the scarlet tanager; the catbird; Phœbe; Jenny Wren; the tiny chipping sparrow; the vireos; and many other familiar warm-weather friends have also journeyed southward.

The bare trees and the ground brown with fallen leaves have to some a bleak and dreary look, but this is because a wrong impression has gone abroad concerning them. Nature in winter is not dead, not even sleeping; she is all the time storing up energy to enable her to greet the returning sun in her very best dress. If you will look carefully at the bare limbs and branches of the trees and bushes, you will see the little buds that are slowly but surely swelling up with the pride of young, active, vigorous life, only waiting, with the great patience of Nature, for the proper and suitable time to break away from their winter retirement and take up their part in the new year.

Some of the pleasantest days I have ever known in the open have been spent in the winter woods, when the snow was on the ground and everything _seemed_ still and unfamiliar. Every little sound is accented on a cold day, and the creaking of a swaying limb or the note of a bird comes to you with almost startling distinctness. Somehow you feel on such days that you are more a part of the things about you than in the full flush of summer. It is like meeting people stripped of all the artificial distinctions of clothes and position.

There is something fine in the way the trees stand up in winter; no one can fail to understand what is meant by the “sturdy oak.” They seem to feel pretty much as you do, and show a spirit of vigorous resistance and power to enjoy and cope with the worst that Jack Frost can bring, and the bright sun sends the sap tingling through their limbs just as it does the blood through yours. One day especially that I remember in Central Park brought me a somewhat novel experience, and gave me the privilege of transferring some old bird acquaintance to the list of my bird friends. It was after a fall of snow, and the air was crisp and sharp, indeed it was nipping, and standing still was a chilly occupation. From long familiarity I knew just about where to go to find certain birds, and I was not disappointed in my hunt. My overcoat pocket, it is needless to say, was fully stocked with peanuts and a box of bird seed, and demands were very soon made upon the peanut supply by the fat and friendly gray squirrels that come bravely up to your hand to be fed. They have a most attractive and appealing way of approaching you. The more timid ones stop often to sit up inquiringly, and put one hand on their heart, as if to stop its excited beating.