Omaha Daily Bee Newspaper, August 22, 1915, Page 19

] 1 o W |‘,[ | Tl ff Cross Section of a Thunderstorm. (A) Rising Hot Air Currents. (B) De- cending Cold Air Currents. (C) The Storm Collar, a Constriction Which Produces Violent Winds. (8) The Roll Scud, or Hot Air Driven Upwards by the Cold Descending Current. (D) Wind Gust. (H) Hall Produced by lce Particles Blown Up and Down in the Cloud. (T) Where the Thunder and Lightning Appear. (R) Rain in the Thunder Cloud (R1) Rain Produced in Adjacent Cloud. Science at Last Penetrates the Mystery ., of Cyclones, Tornadoes, Cloud-Bursts, Thunder and Lightning, Which Have Heretofore Been Mysteries e Many features of this familiar occur- rence have not been clear even to sclen- tists, and Professor Willlam J. Humphreys, the well-known meteorologist of the United States Government, has recently furnished some interesting information on the sub- Ject. The rain of the thunderstorm occurs because the earth, heated much more rap- ddly than the upper air on a hot Summer’s d: ends a violent current of hot surface a to the upper region. This current gathers moisture as it rises, is finally cooled, and then falls in the form of rain. Why thunder and lightning ompany the storm is a more obscure tter, and 4s explained by Professor Humphreys by a description of a recent experiment in Swhich a minute thunderstorm was pro- duced. The experimenter allowed drops of distilled water to fall through a vertical last of air of sufficient strength to produce spray. From this the following facts were ascertained: 1. The breaking of drops of water Is accompanied by the production of both negative and positive fons (the particles of which electricity is composed). 2, Three times as many negative ions as positive are released. Now this experiment closely reproduces the conditions that produce a thunder- storm. Such a storm is characterized by . strong upward currents of hot air, and these are strong enough to account for the breaking up of all rain drops which would otherwise fall through them. Hence at the top of the uprushing air current of the storm, 1. e, within the thundercloud, a rapld electrical separation goes on, the first result of which is positively charged rain drops and free negative particles, The positive charges of the rain drops are con- tinually increased by the successive divi- sion and union of the drops. These posi- tively charged drops fall to the earth when- ever the air current becomes weak enough to permit their passage. The negative particles are carrled up into the higher part of the cloud, where they unite with the cloud particles and facilitate their formation into negatively charged drops. These ultimately fall in the gentler rain of the storm. The reunion of the two separated forms of electricity produces lightning Any weather condition in which a layer vi warm air is beneath a layer of cold air is llkely to give rise to a thunderstorm if the temperature contrast be strong enough. Such a situation is unstable and leads to the violent moving about of different strata of the air, which is the essential teature of a thunderstorm The storm may e from intense local g of the earth’s surface, in which s as a local or heat thunder- 1 the over-running of one inother at a different tem perature. Thunderstorms may also result from the under-r ing, and consequent uplift, of a saturated layer of air bv a denser layer Non-local ty] 14 clagsified by the wea fiowing in from all sldes, rising, cooling by expansion, and building up the thun- dercloud. As a result of this process rain is formed at a considerable altitude where the air is quite cold—in fact, so cold that hail is often formed. This cold rain, or & combination of rain and hail, as it falls to the earth, chills the air all the way down o the ground, partly as a result of its low temperature at the start, and partly he- :ause of the evaporation that takes place during its fall. This cold current of air is correspondingly dense and becomes a strong downward current. The frictional drag of the falling rain is an additional factor in giving it this downward mqve- ment The current plunges down and at the same time is carried forward by the gen- eral movement of the storm, under-runping and buoying up the warm adjacent air in front. This current is a typical thunder- squall, which rushes forward from an ap proaching thunderstorm, agreeably coolinz the air, Between the uprising sheet of warm air and”the adjacent descending sheet of cold 1ir horizontal funnels are formed, in which he two currents are more or less mixed. I'hese become visible at a point pear the thunderstorms are front lower edze of the main thundercloud, experts as cy- where the rising air has so nearly reached - T or frc storm, layer of alr by he clonic, tornadie, clonic and border rain point that the somewhat lower thunderstor : to their position mperature produced by the admixture | with resp ) H 1 anti-cyclonie of the descending cold air is sufficient to formaticns t " re. A line or vproduce a fog-llke condensation. This row of to e st xtending from a constitutes what weather experts call a eyclonic centre constitute the wellknown “sauall cloud” or “roll scud.” “line squall.” These are the stages of a thunderstorm On land thw 18 occur most fre- in order: (1) An abrupt fall of tempera- quently in the ea fternoon and in Sum- ture, due to the rain-cooled descending re 0 re at irrent; Thig is because the the air as com- pared with land 1\ water at the two seasons is reversed. Thunderstorms are more frequent in warm and wet years than in cold and dry ones. Heat is the determ- (2) a sharp rise of barometic temperature, which Professor Humphreys believes to be due to lower temperature, decreasing humidity and other more ob- soure factors; (3) a violent gust of wind or thunder squall, already referred to; and (4) initial heavy rain of the storm, mer, and a night and i relative t ducing them, and con- The pame of “rain gush” is given to a sequently most frequent at the sudden acceleration in rainfall immediate- period of minimum sun spots and least !y ‘ollowing a heavy clap of thunder. The frequent at times of maximum sun spots. ex; .nation is that excessive condensation Professor Hu.aphreys explains the struc- ture of a typica! thunderste interesting manner. First in tue thunder cloud leads to a local ex- cess of electrification and electrical dis- charge, since the latter processes depend upon the presence and abundance of water e erAlfernoons e der Stor, ) °d \ How the High Buildings of New York and the Narrow Streets Between Them When Superheut;d in Summer Cause Particularly Violent Thunderstorms. PueTas @ Browe BROS, Photograph of a Thunder- | i | 1 storm Irops Hence excessive condensation or rain formation really precedes the thunder slap, but as sound travels faster than rain falls we hear the.thunder before the rain gush reaches us When the descending current of rain is very heavy, the drops being so large and close together that they form an almost continuous sheet of water, we have what is known as “a cloudburst.” They usually occur over very dry sections of country which have sent an unusually strong hot- air current rushing up into the cold-air reglon. Cloudbursts are often very de- structive, especially in hilly country, where the entire fall of water flow suddenly into the nearby valley, Hail, which is a phenomenon of severe thunderstorms, consists of roughly con- centric layers of snow and ice. It can only be formed in the upper part of a thunder cloud, where both snowflakes and excessively cooled water drops are present. The nucleus of the haflstone having been formed in this cold region gets into one of the upper weaker updrafts of the storm and fall= to the level of liquid drops, where its own low temperature enables it to gather a coatinz of ice. Presently a more violent upward puff carries it aloft azain, and it acquires a coating of snow. This process may be repeated several times, until the hailstone is too heavy to be supported by endiny currents and falls to earth RNecent photographs of the lightning flash by selentific observers have done much to elucidate the real shape of this startling rhenomenon. It is now known that the old, popular and artistic concep- tion of a zig-zag streak of lightning is mis- taken, and that the flash has several typi- cal forms, all quite different from this con- ception, The fact is, of course, that a Mghtnin= flash is so dazzling that the hu maé canr obtain an accurate im- pression of it. The photographs show that most often the lightning flash fills itself up gradually, and consists of several successive dis- *harges along the same path. The dis- charge differs from that of an electrical machine ip one important respect—the dis- tribution of the charge. In the case of the machine this takes place almost wholly on the surface of the apparatus, while in that of lightning it is frregularly distrib- Copyright, 1015, by the Star Company. uted throughout the cloud. In both cases, however, the air must be charged with particles of one kind of electricity before the discharge can take place freely, This condition at times seems to establish it- self gradually. According to Professor Humphreys's view the lightning spark, once started, “lonizes” the air and makes its own con- ductor as it goes. A similar condition can be produced on a photographic plate by bringing in contact with the film some dis- tance apart two conducting points attached to the opposite poles of an electrical ma- chine. “Brush” discharges develop about each point, but the glow at the negative pole detaches itself and slowly meanders across the plate toward the positive point. This explanation furnishes a possible clue to the cause of “rocket lightning,” which is a flash progressing slowly across the sky line a sky-rocket and of “ball light- ning.” Professor Humphreys has Investigated the question whether lightuing is unidirec- tional, i. e, flowing in one direction or oscillatory. He has come to the conclu- sion that it 1s unidirectional, for the fol lowing reasons: (1) Lightning operates telegraph Instruments; if these discharges were alternating it would not be so; (2) at times it reverses the polarity of dyna- mos; this requires a direct and not a high- frequency alternating discharge; (3) the oscillograph shows each surge or pulsa- tion, as well as the whole flash, to be flowing in one direction. If the day grows excessivély warm and toward evening the clouds seem to rest on the western horizon and become grayish at the base, If the wind dies away and the atmosphere seems unusually qulet, it is the best evidence of a coming thunder- storm. Thunderstorms are more dangerous over waterways than over dry land, because water is a good conductor of electrieity. Over a river the lines of electrical force are concentrated between the low-lying clouds and the water, which creates an electrical disturbance of greater energy than is observed over the land. ‘Remarkable Lightning Effects Photographed During a Thunderstorm at Sea. A cyclone occurs at an area of low pres- sure—that {s, where the atmospheric pres- sure is least, or where the barometer reads the lowest, and is nothing more or less than a comparative vacuum in the atmos- phere, into which the winds from all sides blow. The eystem of winds established by blowing toward the low-pressure centre is called the “cyclonic system,” for the rea- son that they blow spirally inward and up ward, with a motion contrary to the direc tion of movement of the hands of a watch, and when nearing the centre the spiral motion becomes more pronounced. The storm centre s known by sallors as the “eye of the storm.” At the centre of the cyclone the atmosphere for an hour or two in the most extensive storms be- comes clear, the clouds disappear, the barometer shows a slight rise, and to all appearances, except to the experienced ob- server, the storm Is practically over. This condition changes after the storm centre passes, when the wind shifts from the easterly quarter from which it has been blowing to a westerly one and attains a greater force. This peculiar phenomenon is due to the ascending current of air at the storm cen- tre being dissipated by a descending cur- rent from higher altitudes, thus prevent- ing the formation of clouds at that point, The tornado is the smallest and yet the most powerful and destructive of all storms. It is of local origin, limited in width and length of its path. Its chief characteristic is a funnel-shaped cloud, which dips to the earth’'s surface and has a violent rotary motion. The upper surrounding sky fis covered with a mass of black, treacherous- looking clouds. A tornado and a cyclone are very different formations, and are only alike in that each ig a storm of whirling motion. The cyclone is a wide-area storm, covering five hundred to two thousand miles, with brisk to high winds extending from its centre to its outer edge. The tornado is only from fifty to a thousand feet wide and usually travels a distance of one hundred to two hundred miles be- fore it is dissipated. The explanation of a tornado is that when an area of low pressure passes over the country the general circulation of winds from all sides flows toward its cen- tre, which brings the colder, dry winds from the north and west, and the warmer, molst winds from the south and the east into the general circulation of alr bearing toward the storm centre, It is believed that in this rush of warm and cold air there must be a point of meet- ing where there is a great difference of temperature. In this general case the war- mer current underruns the colder layers of alr, and In seeking an outlet forces its way through the place of least density, causing a violent upsetting of the atmos- phere, which results in the formation of a funnel-shaped cloud of condensation of moisture from the uprushing of warm, molst air. The greater the difference in the temperature between the warmer and colder air layers the greater will be the violence of the rotary motion which takes place at the vortex. A tornado as it advances produces a ter- rible roar, which has been compared to the nolse of thousands of trains of cars pass- ing through a tunnel at the same time. This terrific noise usually occurs about fifteen minutes before the arrival of the tornado, and gives warning of its approach. It s probably due to friction caused by the violent rotary motion of the tornado fun- nel. No power has ever resisted the force of a tornado except a mountain range. To be within the tornado path is almost cer- tain death. On the south side one may stand within a distance of five hundred feet with impunity, but on the north side it is almost certain destruction to be with- in a thousand feet. The tornado uproots trees, blows down houses, lifts bridges and large buildings from their foundations, blows trains of cars from their tracks and lifts them several feet in the air before overturning them. Why Many Go-Carts Are So Bad for Babies HE cholce of a vehicle for the baby T is a matter of great importance. The folding cart, which may be taken on the street cars, permits mother and baby to go out many times when it would not otherwise be possible. The great convenlence of this cart cannot be denied, but such cars should be used only for the purpose for which they are intended, namely, to ccenvey the baby short distances, and not as pleasure veh- icles, nor should the baby be left to sit fastened in one of these small carts for any great length of time. Some of the go-carts of the present day are so small, so stiff, and so {ll adapted to the baby’s anatomy that they can Great Britain Rights Reserved hardly be recommended even for tem- porary use. Also, they are so close to the ground that the child is propelled through only the lower and colder air currents, which fling an unending stream of germ-laden dust off the street into his face. They frequeatly have no cover with which to shield the baby from the heat or cold, or sun or wind, and in cold weather it is impossible to keep a baby sufficiently warm in one of them. The best vehicle for ordinary use about the home is one which i3 at least two feet high. It should have room for the baby, with the necessary wrappings, in any position, and a cover that can be readily adjusted to secure the needed protection, It should have strong, well-balanced springs and stand squarely on four wheels. A safety strap which fastens about the baby's waist gives greater pro- tection than the ordinary carriage strap. Carriage outings are, at best, not an unmixed advantage to the baby, although often they afford the only available means of his getting the out-of-door air. The lack of exercise and the more or less rigid position maintained for considerable periods of time serve to tire the baby. Also it is no doubt true that a baby sent out in charge of another child or of some person not altogether competent to Judge of his comfort is often neglected. A more wholesome and natural place for the baby to take his airing is in the yard or on the porch, where he can be under the mother's supervision.