Popular Science Monthly/Volume 53/May 1898/Kite-Flying in 1897
|KITE-FLYING IN 1897.|
ONE of the most noticeable movements of the present time in popular science is kite-flying, while its practice as a pastime is having a large increase. Its interest to our reader, however, is almost wholly in its scientific aspect.
To the question, What is really the use of all this practice with kites '( Mr. H. H. Clayton, superintendent at Blue Hill Observatory (in the suburbs of Boston), once replied nearly as follows: "We are living in an atmosphere of which we practically know very little. Our position is like that of crabs at the bottom of the sea. It is expected that such knowledge will be gained in these aerial explorations as will enable the meteorologist to predict hot and cold waves and the various kinds of storms more accurately and much earlier than has been done heretofore. The observations have already become serviceable in this direction, while the knowledge gained has modified opinions found in the text-books."
Truly there are mountain tops three, four, and nearly six miles high, but these are remote or inacessible; besides, the atmosphere enveloping them is mainly of the same stratum which rests upon the surface of the earth elsewhere, only a little rarefied, chilled, and broken in upon slightly in storms, when the stratum is shallow, by the more rapidly flowing stratum next above; so that usually what may be found on the mountain peaks is merely the crest of a billow of the lower atmosphere.
The pioneer in scientific kite-flying in America, in the recent period, is the Blue Hill Observatory, in the suburbs of Boston; and here, too, the highest flights have been made.
It is not asserted that there have not been other successful experiments with kites, but that the results of those at Blue Hill are in advance of all others in the field of meteorology. Mr. E. Douglass Archibald, in England, has made experiments with a kite and anemometer, and is the inventor of the improved tail, which has
|A Train of Tandem Kites bearing a Meteorograph.|
cup cones instead of bobs; while Mr. Hargrave, an Englishman in Australia, there invented the valuable type of kite which bears his name. In America, Prof. C. E. Marvin, Mr. A. W. Potter, and others, of Washington; Mr. William A. Eddy, of New Jersey; and Mr. G. T. Woglom and others, of New York, have all done valuable service. Professor Marvin is the author of the two pamphlets of valuable technical investigations in relation to kites, issued by the United States Weather Bureau. Mr. Woglom, also, has published a valuable treatise on parakites, while Mr. Eddy has devised the excellent kite connected with his name.
The first attempts at Blue Hill were with the Malay kite—the prototype of the Eddy kite. Mr. Eddy claims, however, that his bird-form kite is the result of his own study and experiment, before he had exact knowledge of the form used by the Malays and Javanese.
The descriptive term, bird-form, has reference, not to the outlines of a bird of any kind, but of the proportions of width to length in a kite, as comparable to the length of body and spread of wings in a bird. In the Malay kite the cross-stick is almost as long as the backbone; in the Eddy kite it is slightly longer. The Malay crosspiece is permanently formed to the shape of a Cupid's bow, the central arch to the wind, thus pressing out the covering in a wide keel; in the Eddy kite the cross-piece is slightly bent by a cord, like the simplest form of archer's bow. All kites of the Malay and Eddy type are intended—unlike the common kite—to fly without a tail.
It was doubtless in the island of Java and in the Malay Peninsula that kite-flying had its earliest and greatest development. The practice appears to have spread from these countries to China and Japan, where the forms are greatly varied and the uses extended.
In China the notable forms are the dragon kite and the bird kite. The first is composed of a large painted disk representing a horrible head, drawing two lines of smaller disks diminishing to the tail, where they unite in a tuft of some sort; each disk being also connected with one opposite in the parallel row. This basal form is diversified by various treatment.
The frame of the Chinese bird kite is generally made up of bamboo splits in loops, joined in rude, conventional imitation of the body, spread wings, tail, and head of a bird. This kite is often provided with a musical attachment in the shape of a hollow section of bamboo pierced with holes, or furnished with reeds that are vibrated by the wind. When mounted high in air, the tones proceeding from it resemble those of an æolian harp, and can be heard at a great distance.
Chinamen have a superstition that both these forms of kite are a protection to the family against evil spirits—the first, by frightening them away; the latter, perhaps, by abashing them by its harmonies, as those which infested Saul were influenced to depart from him at the sound of David's harp. Sometimes these kites—the cord being securely fastened—remain aloft for several days and nights; the family meanwhile enjoying an unusual sense of security.
Kite-fighting is also practiced in the vicinity of the cities and larger villages. This sport consists in tearing the kite of a rival or cutting the line; the first, by means of long wooden knives attached to the assailant's kite; the latter, by small fragments of glass mixed with glue, as a coating for the upper portion of the line. All Chinese kite-flying, though skillful, is in some feature barbaric.In Japan the kite-forms indicate a more practical character in the makers. The kites are shaped to represent many kinds of animals—quadrupeds, birds, and fishes. When in the sky, these kites might convey information quite a distance to acquaintances who could recognize them and thus know what family was represented at the other end of the string; for in Japan the sport is
largely social. A recent announcement comes as a surprise to everybody, that the, Japanese records prove that six hundred years ago kites were used by this people in war time for carrying up observers to detect the position of an enemy's forces.
After all, America must be credited with the first application of the kite to scientific investigation; Ben Franklin—as all intelligent persons know—being the experimenter from whose discoveries large results in electrical science have proceeded. Numerous experiments in this direction followed his initiative, in France and, with less fervor, in England; while in Russia a zealous scientist lost his life by his temerity with a metallically equipped kite in a thunderstorm.
Perhaps this catastrophe was the cause of the abandonment of this method of investigation of the upper atmosphere, for nothing that attracted much attention was again accomplished by kites until the year 1894, when the Blue Hill investigations began.
The first year's work at this observatory (a private institution, established and sustained by Mr. A. Lawrence Botch, from public spirit) made little addition to the knowledge previously acquired by amateur fliers; but the succeeding years show marked advances.
At present it is usual, in flying flat kites, to send up several on the same main line. Generally a small kite is first sent up, and, when this is securely mounted, a larger one, attached to the main line perhaps a hundred feet below by about that length of its own string, is started after its leader.
As the number of kites in the tandem increased, more strength was required at the lower end of the line to withstand the pull; so the reel quickly became an important part of the apparatus. The labor of winding was such that the reel was provided with a crank, and mounted more and more strongly, and a recording wheel and dial were soon added to measure the line as it ran out. The apparatus was then made portable by combining it with a sort of wheelbarrow.
Not only the number of kites but the height of their ascent increased the strain on the wheel, and one after another—though of solid oak-—were crushed by the drawing of the concentric layers in winding in, especially after the change was made to a metal string.
Last season (1897) a unique reel was introduced in which a two-horse power steam engine took the place of human muscle for winding in. Steam is supplied by a boiler heated by oil spray as fuel, these and the reel proper being mounted on the same portable base. Included in the winding apparatus is a strain-wheel around which the wire passes four or five times, running from this to the drum of the storage reel—on which it is wound lightly and evenly by automatic action. The wire comes in from and goes out to the kites over a pulley, which turns so as to deliver it 111 any direction to them. There is also a wheel which records the pull of the line, and a provision for recording the measurement of length. Thus the relation of wind pressure to pull, and several other matters, can at any minute be figured out.
The purpose of the observatory from the first was to secure by means of kites a more elevated plane of observation than could be obtained by other means. As soon as the corps had acquired skill in kite making and flying, a self-registering thermometer was sent up; afterward they were able also to add a barometer, these being carried on a base, covered by a wire basket, and attached to the line as high among the kites as it could be sustained.
But the two instruments did not furnish a record of all the elements; and finally a complete "meteorograph" was devised. Externally, this was a cage of wire one foot in height, the same in width, and half that in the other dimension. The weight of a similar one used in Washington is two pounds and a half. The combination within consists of a thermometer, barometer, hygrometer, and anemometer—all making record on a sheet of paper wound on a cylinder that is revolved by clockwork. As the direction of the wind is ascertained by the drift of the kites, each flight furnishes the observers with five meteorological elements. No doubt they will be able ere long to determine the electrical conditions at different heights with equal accuracy.
Every well-constructed kite has a fixed capacity for ascending to a certain height—not more than a few hundred feet usually, because of the increase in the weight of the line and the wind's pressure on it; therefore, in order to reach a greater altitude, it became necessary to connect another kite to aid in the lifting. Still higher flights required a further addition of kites, until sometimes a dozen, ranging in size from five to twelve feet, were up in the same tandem, requiring a small rope to hold them. A large and divided wind surface was necessary, else in lulls the kites would descend and the instruments with them; so the obtaining of observations was at great cost of time, labor, and money. In a fresh wind the vigorous efforts of three strong men were required for two or three hours to bring a large tandem down. Several times, in strong winds, the kites have broken away, only reaching the ground two, four, and nearly six miles distant; yet nearly every time they have been recovered without having sustained much damage.For the reason mentioned on a previous page, some two years since, No. 14 steel music wire (the size of small piano strings) was substituted for the line of vegetable fiber. A mile of this wire weighs from twelve to fifteen pounds, which is much lighter than
|Eddy Kites||Multicell Kites||Hargrave Kites||Blue Hill Bird Kites|
|Kites flown by Mr. J. B. Millett, Sharon, President President of Boston Aëronautical society.|
the bulky flaxen cord previously used, and it offers so much less resistance to the wind that two kites on a wire line will bear the instruments to as great a height as six of the same size on a flaxen line. Still, owing to weight and wind, the droop in the wire is so great that about two miles of it are required for one mile of ascent.
The wire had also some disadvantages, one of which was rust. This has been overcome by an arrangement by which oil is dropped upon it as it is wound in. Another difficulty last year was the startling shocks the men holding the line got from the electricity it
brought down from the sky; but no handling is now required, and the machine carries all the sparks harmless to the ground.
No attempt is yet reported on the part of the Blue Hill people to investigate specially the electrical phenomena since those by Mr. Alexander McAdie at this observatory in the summer of 1885, and again in 1891 and 1892; but certain gentlemen near New York, assisted by Mr. W. A. Eddy, on the night of November 13th, sent up by means of kites an electrical collector (presumably a plate or wire net of copper), a small copper wire forming the conductor. The first spark was obtained between fifteen and twenty-five minutes after the kites were sent up, and when the collector was at a height of three hundred and eighty-one feet. The time was between ten o'clock and midnight. The temperature at the earth's surface at the time was 38° Fahr., while a self-registering thermometer sent up on the kites showed 37° at an elevation of four hundred and twenty feet—the sky being clear, or nearly so. Quite likely the records of electrical phenomena at Blue Hill are more full and explicit than this at Bayonne, but neither these nor the theories on the subject have been given to the public.
The first practical use of electricity obtained by means of kites, so far as 1 have learned, is in the wireless telegraph system of Signor Marconi, in which the collectors at the poles are kites of thin copper, these being connected Showing ring at the upper end of the wire line to which are attached the strings of two kites, also the cord bearing the meteorograph. The two round objects at the bottom represent the two round cups of the anemometer. by small copper wires to either the receiver or the transmitter, on the ground. Though Marconi claimed to have sent readable signals twelve miles. Superintendent Preece, of the English Government Telegraph System, in endeavoring to duplicate these successes, was unable to obtain a satisfactory result at a greater distance than two or three miles.
The experiments at Blue Hill have shown a difference in electrical conditions at different heights, and in different conditions of the atmosphere in respect to temperature, humidity, and movement; and there seem good reasons for confidence that ultimately this element will yield valuable results in more than one direction.
It is not improbable that if metallic kites could be sent up to the verge of some higher stratum of the atmosphere, where the contact of the diversely moving strata sometimes evolves noticeable auroras, some considerable electric charge might be obtained for telegraphic or telephonic transmission, and, possibly, by storage, for light and power.
In considering the various phenomena of kite-flying, however, we must not neglect the kites themselves. The effort of the scientists has from the first been to find a form which would give readiness of ascent, steadiness in flight, lifting power, and capacity of reaching great altitudes, together, of course, with mechanical stability and endurance under all conditions. Because of their necessary slenderness, and their delicacy of adjustment for balance and pull, all flat kites have been found precarious; consequently, not meeting requirements except in the best weather; besides, so large a number are necessary in light winds to carry up the instruments to the desired elevation, involving labor and time, that the cellular kites are becoming the chief reliance for meteorological observations aloft.
The antetype of all these is the Hargrave pattern, invented by an Englishman of that name in Australia in 1894. All are remarkable for their lifting capacity, and generally for their ready ascent. The Hargrave consists of a light frame, outlining a box, about which, at each extremity, is a wide band of cloth, the frame being bare at the middle section. In proportions, a rectangular cell six feet long is usually about the same in width, and one fourth as deep as it is wide. There is much variation in most features of the box kite, as made by different fliers. The bridle is attached to the two lower corner bars nearly midway of the length or the four lower corners of the uncovered section, or otherwise, according to form and use.
For use at Blue Hill, observer Clayton devised a modification of the Hargrave, consisting chiefly in the narrowing of the box, and a different framing.
Another form of the cellular type is the diamond kite of Mr. S. A. Potter, of Washington, D. C, whose device has a square instead of an oblong aperture, and has the bridle on one of the longitudinal angles, so that it flies with a corner, instead of a side, downward. To this another Washington inventor has attached a pair of triangular wings, which is said to increase the lift very much, leither of the forms of Hargrave type bears even a suggestive resemblance to the common kite.
Still another cellular kite is that constructed by Mr. J. B. Millet, president of the Boston Aëronautical Society. Except by a diagram, an idea of this kite may be best conveyed by saying that, in the main, it is a Hargrave cell doubled, or having a third wall inclosing a superimposed cell; a development which might be carried on indefinitely. It is nearly the same form as the flying machine, carrying and operated by a small steam engine—the invention of Professor Langley, of the Smithsonian Institution.
I am not aware that the lifting capacity of any kite has been submitted to so striking a test as on the Hargrave until the present season. Two of these, on November 12, 1894, in Australia, are reported to have borne the inventor up sixteen feet; and in 1895, by the same number, he is said to have been lifted forty-five feet. Subsequently, Captain H. Baden-Powell, of the Scotch Grays, in England, was carried up one hundred feet by a tandem of the same type. On January 21, 1897, Lieutenant Hugh D. Wise, of the Ninth Infantry, United States Army, was lifted in a boatswain's swing suspended from four Hargrave cells to a height of forty-two feet above New York Bay.
The later instance referred to is thoroughly verified and reliable. It is the ascent made by Mr. Charles H. Tamson, near Portland, Maine, on June ]9, 1897, to an elevation of fifty feet with a single kite of the form devised by him. In most other exploits of this kind the aëronaut has been drawn up by a pulley to kites already well poised aloft; but Mr. Lamson Meteorograph. started with his kite, running along on the ground as it was drawn forward, and going up with it when the initial impulse had been gained. The Lamson kite is constructed on an original idea, though it is a combination of the flat and the cellular types. The gain in height of ascent by kites since experiments began at Blue Hill has been at the rate of about one thousand feet each year. The highest ascent previous to 1897 was made by a six-foot kite of the Malay or Eddy pattern, on October 8, 1896. The elevation attained was 9,400 feet above tide-water, 9,300 feet above the surrounding country, and 8,770 feet above the top of Blue Hill, which is 635 feet above the sea—in full view from its summit. The meteorological instruments made records up to a height of 9,375 feet.
A higher ascent was made early in the autumn of 1897 at Blue Hill, when the leader of a tandem, a Lamson kite, reached an elevation of 11,060 feet (two and a tenth miles), where it was broken by the strong wind. The observatory people now hope that, with the Lamson kite as a leader, they will be able to send their instruments to a much greater height.
The elevation of the kites is determined by the same means used for mountains—the pressure of the atmosphere as recorded in the barometer, and calculations with the angle the kites make with the extremities of a base line. The string has too much indeterminate sag to furnish an accurate measurement.
It has been found that with an increase of altitude a constantly lowering temperature is encountered, except rarely, when there is an overlying warm stratum, ushering in a spell of unseasonably warm weather. At the approach of these warm tides, when the kites ascend they find, as usual, a decreasing temperature for a while, but it suddenly rises as the instruments enter the radiating waves of caloric—sometimes as many as seventeen degrees. In advance of and during cold waves the temperature falls uniformly and rapidly in the ascent. Observations at Washington, New York, and Blue Hill coincide in showing that approaching warm and cold waves are perceived, at a height of a thousand feet or more, from six to twelve hours earlier than their prevalence at the surface of the earth. One reason for this is that the air moves freely and rapidly at the height of a few thousand feet, while it meets with many obstacles below.
There is an interesting bit of information from the kites for us in regard to Boston's much-denounced east wind—though in the heated term it is generally quite a relief. It has been ascertained at Blue Hill that these chilling inflows begin at the surface and thrust themselves wedgewise under the local stratum, working upward. At their greatest expansion, however, these eastern winds rarely have a depth of more than twelve hundred feet.
At the surface of the earth, as every one knows, there is usually a marked increase of the temperature during the day, and a decrease at night; but at an elevation of three thousand feet this variation disappears entirely, the days being there as cold as the nights. The changes of temperature aloft are very large, but they are not diurnal. At this height, also, the days are marked by a damp atmosphere, while the nights are dry. This is simply a phase of the dewfall, and to a degree also of the clouds and the rainfall.
The behavior of kites in the vicinity of cumulus clouds is peculiar. When one of these tracts of snowlike baseless hills sails calmly over, the kites ascend more or less rapidly toward it, often following as far as the line will permit. Every observer has remarked the rounded shapes of these fair-weather clouds, like high upheavals of condensed steam; and it has long been held that they were the result of—or, at least, attended by—upward eruptions of air, perhaps from heat expansion.
The nimbus cloud, from which most of our rainfall comes, has little effect on the kites other than disqualifying them for flying because of wet. Kites usually find little or no obstacle in the stratus. Among the memoranda of flights is noted, of one such passage in summer, the emergence of the kite above a cloud of this kind of a computed depth of five hundred feet. The hygrometer showed that in the midst of the cloud the humidity was one hundred per cent—full saturation; so that a slightly cooler wave of atmosphere would have caused precipitation; yet above the cloud the atmosphere was quite dry.
In the colder seasons of the year the kites would usually have come back from such passages beautifully iced in minute crystals. In an observation made in October, 1896, the box of instruments, at the height of three quarters of a mile, entered a cloud from which
it emerged at an elevation of about a mile. The record showed that close under the cloud the temperature was just below freezing; above the cloud the atmosphere was very dry; and at the limit of the ascent (9,375 feet) the temperature was twenty degrees below freezing.
Probably the most striking thing in recent kite-flying is the making of photographic views by a camera in the sky, borne up by kites. Mr. William A. Eddy has claimed to be the pioneer in this field, having taken views from kites on May 30, 1895; while Messrs. G. T. Woglom and George E. Henshaw, of New York city, claim that the first good picture from a camera sustained by kites was made by them on the afternoon of September 21st, following.
There are several ways in which a camera could be carried up, and operated from terra firma. Mr. Eddy sends it up with its bearer attached to the strings of as many as three kites. The apparatus consists simply of two spars about the length of a trout rod, and of about its size at the butt, the end of one spar being joined firmly to the middle of the other; and on this junction the camera is mounted. A cord looped along the trunk line controls the slide of the camera. Many excellent pictures have been made by these means.
Kites have been used, also, for sending up colored lights for signaling; while by an ingenious use of a large and somewhat modified camera, views of objects at a distance have been presented to observers on the ground, when such objects would have been otherwise invisible to them. Thus the operation constitutes a sort of artificial mirage, which, very likely, will not always be without its uses.
It may reasonably be expected that kite-flying will, in the early future, become one of the most common pastimes, as it has already become a scientific pursuit at many places; being specially adapted to certain situations, as islands and upland regions.
On the Isles of Shoals, off the New Hampshire shore, during the last season there was a very elegant kite carnival. Nearly one hundred kites were there, mostly in the hands of children. The larger number were of the Clayton cellular pattern, but of small size. On one occasion sixteen of them were flown to a great height in a single tandem. Each kite was differently marked, by color or other means, so that these alone afforded a very pleasing spectacle, without regarding the delighted children and their maturer companions beneath.
Kites in tandem, unlike members of equine and other tandems, are rarely if ever in line, but diverge irregularly, like the branches of a tree. This is owing to variations in the flow of the atmosphere, which appears to be less uniform than the currents in a river, having eddyings, swervings, and evanescent accelerations and retardations.
Aside from the charming groups watching their progress, there is pleasure for any observer in a flight of these ethereal forms, various in color, dispread from the trunk line as though they were huge leaves or high-flying butterflies on the tips of invisible branches.
The flat kites of the Malay or Eddy type are not less pleasing than their tailed cousins, the common kites of various shapes, and are more like living creatures, because of their incessant action. The mounting up of one after another with irregular movement, now turning to right or to left or downward, then catching an upward-going zephyr and soaring with it at an angle of seventy or
eighty degrees far up after its happy mates, will be watched by the leisureful looker-on with absorbing interest.
Behold them, at length, poised high in air; the position of the far-away leader discoverable only by following with the eye the faint spider thread of drooping line. Ceasing from progress and retrogression, poised like humming birds before a flower, tipping momentarily now one side and then the other in rhythmic movement. changing their tint with every motion, the casual observer has an impression that he is gazing at a flock of real birds, with a notion of white, gray, pink, blue, and purple gulls, uncommonly wide of wing and unusually fascinating.
Now and then one or another sails away from its place and poises itself for a few moments, then returns nearly to its former position; while another takes a sudden dive downward, ending in a graceful parabola which brings it to a new point on its original level. Sometimes one kite will move almost directly at another, which shyly sidles away; when the first ceases its movement, droops, and sinks down, until, just in the nick of time, a strong young zephyr catches it and buoys up its faltering pinions.
The cause of all these apparently purposed movements being invisible to the beholder, some degree of reflection is required to rid one's self of a lurking idea that these are animate things.
Elements of the Hargrave Kites.
From the Tables of Blue Hill Meteorological Observatory.
|No.||Width of kite:
|Length of kite:
|Depth of Cell:
|Width of Cell:
sticks: Square mil-
The lifting surface of these several kites is assumed to be the total surface of the side planes (upper and lower). The sticks have a rectangular or elliptical cross-section.
The kites are very stable, and fly in recorded wind velocities of from six to twenty metres per second. The angular attitudes reached by the first two kites average between forty-five and fifty-five degrees, and those reached by the last two average between fifty and sixty degrees. The pull in a recorded wand of ten metres per second averages about five kilogrammes per square metre of lifting surface.
The Blue Hill method of testing kites is to fly them with a short line, usually from fifty to one hundred metres long, and to make frequentand regular observations of the angular attitude and of the pull. The instruments employed are a surveyor's transit and a spring balance. Tests are usually made under widely varying conditions of wind velocity, and the kites flying at the highest angles and those exerting the greatest pull are easily selected. The work in view consists of raising a meteorograph of known weight under varying conditions.