Popular Science Monthly/Volume 16/March 1880/Frost-Phenomena in Southern Russia
|FROST-PHENOMENA IN SOUTHERN RUSSIA.|
SOME few people may perhaps have remarked and remembered an unusual meteorological phenomenon which occurred in London last Christmas night. We had had several weeks of hard frost, and the cold on Christmas morning was rendered more piercing than ever by a bitter east wind, though indications of an approaching thaw were not wanting. About the middle of the day, snow began to fall; but in the evening this changed to rain, which froze as it came down; and by ten o'clock not only were the pavements covered with a sheet of slippery ice, but walls, lamp-posts, railings, etc., were all glazed in like manner. Every object upon which the eye rested glittered and sparkled, looking as if it had received a sudden coating of glass; while from every roof and ledge hung a fringe of icicles, some of them as much as a foot in length. In the morning, the whole fairy-like appearance had vanished.
This sort of thing does not often occur in England, and, when it does, it lasts but a few hours at the outside; but, in certain latitudes, the requisite meteorological conditions sometimes continue for days and even weeks together, and then the results are most disastrous. The rain continues to fall, and to freeze as it falls; and the crust of ice grows thicker and thicker, until tall trees and miles of telegraph wire are broken down by the enormous weight. Fortunately, the phenomenon is generally arrested before it attains this extreme degree of development, and, when it does occur, seems to be almost entirely confined to the steppes of Southern Russia.
It may be remembered that, during the winter of 1876-'77, frequent references were made in the newspapers to the state of the South Russian telegraph lines, many of which, especially those in the governments of Kherson and Taurida, were rendered perfectly useless for weeks by just such an accumulation of ice as we have been describing. A German gentleman, Herr Bernhard Bajohr, happened to be journeying from Nicolajew to Berislaw about the middle of December, when things were at their worst; and as the phenomena are seldom seen so fully developed, even in Russia, as they were at that time, it may be worth while to give some account of what he saw. His road lay between two telegraph lines; one the Indo-European, the other that of the Russian government, so that he had ample opportunity of observing and comparing the different effects produced upon the two. But, before describing these, we must say something as to the meteorological conditions required for the formation of this peculiar ice-incrustation.
In long-continued and severe frost, the earth is frequently chilled to a considerable depth, and to such a degree that it absorbs the warmth from the lowermost stratum of air, which becomes icily cold in consequence; while the trees, buildings, etc., within the cold stratum naturally share the surrounding temperature. This cold stratum may be from twenty to forty feet in thickness, while the air above is many degrees warmer. If rain fall from these warmer regions, though there will not be time for it to freeze during its short passage through the colder air, yet, directly it touches the ground or any other ice-cold substance, it will congeal and cover it, whatever it be, with a glaze of transparent ice, as noticed above. Herr Bajohr observed that, when the ice first began to form upon the telegraph wire, it was in the shape of a cylindrical roll, which instead of hanging from the wire, or being crystallized round it, as one would have expected, merely rested upon it, the wire touching its lower circumference only. As rain continued to fall, the cylinder increased in size, until its diameter measured from half an inch to three inches. This was the first stage of development; but then the intensity of the cold abated somewhat, and the rain which was still falling, instead of freezing the moment it touched the roll of ice, had time to trickle over it, and form long rows of icicles, remarkable for their regularity and uniformity. This was the second stage, and the heavily laden wires looked like nothing so much as gigantic combs.
It is not often that the third stage of development is reached; but it does sometimes happen that, when icicles and cylinder have attained their full size, the rain ceases, the sky clears, and the sun begins to shine. Its rays are much too feeble to melt the ice; but they pass through it to the more sensitive black wire within, whose temperature is so much raised that it melts the particles of ice in immediate contact with itself; its cohesion with the heavy roll of ice above is destroyed, and the latter, unable any longer to maintain its balance, twists round so as to describe a semicircle and exactly reverse its position. The icicles now stand up in the air above the wire, while the roll hangs below it; and, if there should be more rain, a second row of icicles will be formed opposite the first, producing a striking resemblance to the backbone of a fish, which is rendered still more perfect if there happens to be any wind blowing in the direction of the telegraph line, as in that case both rows of icicles will be slightly inclined toward the wire in the same direction. This last stage of. development may also be attained without rain, should the sun have sufficient power to melt some of the ice; the water from which will then trickle down to the under-side of the roll of ice, and there form icicles in a similar manner. As the sun gains in power, the wire increases in temperature, and melts away more of the ice from within; the icicles, borne down by their own weight, drop lower and lower, until the wire reaches the extreme points of the upper row, when of course the whole congealed mass soon drops off.
Herr Bajohr noticed that the effect produced by this phenomenon on the two lines of telegraph differed considerably, that of the Russian government suffering far more than the other. The posts of the Indo-European line are of iron, and the conducting-wires are thick and strong; and, though the wire was considerably stretched, it had on the whole borne well the immense strain put upon it. Here and there, where the line made a bend, the post at the angle, firmly fixed though it was, had sometimes given way, and, wherever this was the case, several of the neighboring posts had also succumbed. But the government line, with its oaken posts and four thin wires, running parallel with the Indo-European line, presented a much more dismal appearance. The oaken posts, somewhat crooked to begin with, had not all proved strong enough to sustain the weight of the four heavily laden wires, and in some places had broken down altogether; while, where they remained erect, the wires were either broken, or completely weighed to the ground by the burden laid upon them. All the posts, both iron and oaken, were covered on the windward side with a crust of ice several inches thick, reaching from the ground to the insulators, where it joined the ice on the wires; and in this way insulation was destroyed, and each post was converted into a conductor, down which the electric current passed into the ground. This was especially the case directly the extreme severity of the weather abated and the ice became less dry. But the iron posts had this marked advantage over the wooden ones, that, whereas the latter kept their coating of ice for weeks, these others threw it off directly the sun began to shine. Being black, they absorbed heat more readily, and, by melting the inner surface of the ice, soon caused the whole to crumple up and fall off.
In conclusion, it remains for us to say a few words as to the effects of this remarkable frost-phenomenon upon the vegetable world. Trees are everywhere scarce in the steppes, their cultivation being attended with very great difficulty; nor is this to be wondered at when one considers the various climatic influences to which they are subject. During the winter of which we have been speaking, every tree, every branch, every smallest twig was incrusted with ice one, two, or three inches thick; and accordingly the trees in the town of Kherson, chiefly white acacias, lost nearly all their branches, while many of the smaller ones were completely crushed to the earth. Of the fruit-trees, all of which looked as if they were made of glass, some suffered more, some less, according to the character of their growth. The apple-trees and apricots for instance, with their spreading horizontal branches, were for the most part quite broken down; while the more erect-growing pear-trees and cherries, had maintained their balance better and suffered much less in comparison. — Chambers's Journal.