CHAPTER 6

TVeather Prophets
METEOROLOGISTS ARE THE ONLY PROPHETS EMPLOYED by the state, which prefers to leave other methods of prediction, e.g. public opinion polls and economic forecasts, in private hands even when it does make use of them. Weather forecasts, however, are needed by so many people that it is only right to expect the taxpayer to foot the bill.
But though their services have always been in great demand, meteorologists have one of the most thankless jobs imaginable. The errors of other prophets are often overlooked, but weather forecasts can be read and checked by anyone old enough to read a newspaper, and few men are prepared to make allowances when their favourite football game or picnic is washed out despite forecasts to the contrary. Even people whose activities are fairly independent of weather conditions will become terribly angry about false weather forecasts, often accusing the meteorologists of robbing them of a precious day in their lives. This is true even if the promised rain turns out to be sunshine. Men are inclined to remember one false forecast and forget a host of correct ones.
Perhaps all this violent carping is no more than a reflection of the great esteem in which the public really holds its weather prophets, or else it is a relic of those days in the not too distant past when meteorologists used to be quite wrong most of the time. For although weather forecasts fell into the province of most ancient court prophets, scientific meteorology is a very young discipline. It was only in the middle of the 19th century that international weather stations were first set up, and without these stations even the shrewdest local observations were bound to be as good as useless.
Astro-meteorology The reason why scientific meteorology grew up so late, is the
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direct result of its having been reared as the step-child of astrology. Even the greatest minds of antiquity thought it self- evident that weather conditions were governed by the stars, and it never occurred to them that the earth had an atmosphere of its own. The term "atmosphere" — circle of mist — was, in fact, only coined towards the end of the 17th century. Before then the "air" surrounding the earth was thought to be completly devoid of matter.
To the minds of the ancients, clouds, rain, thunder and lightning were all controlled by the gods — in Greece, by Zeus himself. Meteorologia was the doctrine of transcendental and particularly of celestial phenomena — ^not, as we might have thought, of meteors.
The Greeks were nevertheless too shrewd to rely on astro- logical weather predictions, and none of the oracles were expected to prophesy droughts or periods of plenty from the constellations, as, for instance, Babylonian prophets were. If a prince from distant lands absolutely insisted on being told whether meteorological conditions would be propitious for a future campaign, the priests would oblige, but on the whole they preferred to steer clear of this equivocal subject altogether. Even when Alexander's campaigns led to closer contact between Chaldean astrologers and the Greek oracles, the latter con- tinued to give the weather a wide berth, and to stick to less risky horoscopes.
Astrological weather prediction only began to come into its own in the Middle Ages. Forecasts were generally made for months or even years ahead on the assumption that "conjunc- tions" (which could be worked out well in advance with the help of tables) always caused catastrophic weather. It was this assumption which enabled John of Toledo to make the predic- tions which, as we saw, caused universal panic towards the end of the 12th century. Although none of his prophecies, viz. that the conjunction of the seven planets under Libra would cause terrible storms which would lay waste cities and ruin the entire harvest, were ever fulfilled, similar prophecies continued to be made, all based on the same assumption.
Astrological, like other, prophecies, if repeated often enough, must occasionally come true, but astrological weather prophets were singularly unfortunate in that not a single one of their
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28. Title page of one of many pamphlets proclaiming a flood in 1524.
promised catastrophes ever occurred. The greatest sensation, but also the greatest flop, came in the year 1524 when, on the basis of a prediction made in Johannes Stoffler's Almanach 25 years earlier, a great flood was expected on the 2nd February. On that date a number of planets were expected to meet under Pisces. The matter was keenly discussed and no less than 137 pamphlets about it were published. Though some weighty voices objected that God had clearly promised mankind never again to destroy the earth with another great flood, ^ many people deemed it wiser not to rely on a promise made so long ago and to imitate the example of Noah instead. Huge arks were
1 Genesis 9, 1 1 .
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built in Toulouse, and though no provision was made to house "every living thing of all flesh" in them, enough provisions were hoarded to enable many citizens to weather the expected flood. In a number of ports, all available ships were requisi- tioned and the local population quartered on them.^
The Margrave of Brandenburg, who lacked a fleet or enough funds to float an ark on the river Spree, was forced to take his court and most of his loyal subjects to the Kreuzberg, a small hill south of Berlin. Now the Kreuzberg is no Mount Ararat and its 150 ft. peak could hardly have been expected to offer the population much shelter. Fortunately, the astrological gods had once again sounded a false alarm and the Margrave, together with his retinue, could return home without even a wetting. Oddly enough, the whole episode was forgotten only a few decades later, so much so that the great and highly learned Melanchthon, in his public lectures on the usefulness of astrology, supported his arguments with the claim that Stoffler's predic- tions were fulfilled in 1524.
Florentine illumination
But not everyone was as tolerant of astrologers as Melanchthon. Thus the 15th century Italian classicist Pico della Mirandola wrote: "For a whole winter, I have taken observation of daily weather conditions and checked these against astrological predictions. May fate punish me if I do not speak the truth: on the 130 days or more that I made my observations, there were no more than six or seven days in which the weather agreed with what was written in astrological books, "^
Absurd though astrological weather forecasts were, they had the beneficial effect of inducing critics to make regular notes on the weather. While this was a purely negative measure, these records were to lay the foundation of a future science.
The first steps in scientific weather research were taken in
1 Rudolf Thiel: Und es war Licht (Hamburg 1956), p. 67 f.
2 Giovanni Pico della Mirandola: Selected Writings. German ed. by Arthur Liebert (Jena 1905), p. 261.
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29. Evangelista Torricelli, the inventor of the barometer (164S).
Galileo's workshop. Galileo himself had invented the thermo- meter, and in 1643 one of his pupils, Evangelista Torricelli, invented a handy apparatus for measuring atmospheric pressure, the Torricelli tube, which was, in fact, the first barometer. The news about this miraculous tube took Europe by storm, and only five years later, Pascal proved experimentally that atmospheric air could actually be weighed, i.e. that it consisted of matter. However, his ideas ran so much counter to popular belief, that another century was to pass before they were generally accepted. Still, there was no disagreement about the practical usefulness of the barometer, for when the mercury column rose, a clear sky, and when it fell, mist and rain, could generally be expected. As observations proceeded, it became clear that the barometer did not, in fact, work quite as simply
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as all that, and that other factors, as well, had to be taken into consideration.
One of the most striking aspects of barometric weather forecasts was that they introduced realistic concepts of time into meteorology. While astrologers had prided themselves on their ability to make weather forecasts for centuries ahead, the new science concentrated on tomorrow's weather instead. Hours had taken the place of eons, and weather forecasts had become less fantastic, if less imposing. Thermometers and barometers had found their way into most households, and now even the most illiterate people could foretell (or thought they could) the temperature and next day's weather, and act accordingly.
The three great L's
Professional meteorologists were the first to suffer, since their services seemed to have become redundant. Then three famous French scientists, Lavoisier, Lamarck, and Laplace, began to repair the damage. Unlike the three great B's of music — Bach, Beethoven, and Brahms — the three great L's of science were contemporaries — all three were born in the 1740's — and close friends. They came to meteorology by quite different paths: Lavoisier from chemistry, Lamarck from botany, and Laplace from astronomy.
The first start was made by Lavoisier, who set up a chain of weather stations in France from which he received regular reports. Lavoisier became a very wealthy man, when the French government rewarded him for his scientific experiments by appointing him one of hsfermiers generaux and commissioners of powder. This sinecure was to prove his downfall, for the French Revolution sent everyone of the 28 fermiers generaux to the guillotine. No exception was made for Lavoisier for, as the prosecutor-general put it, the republic needed no scholars.
Lavoisier's death was at one and the same time the defeat of the first attempt to set up a scientific meteorological institute. Lamarck lacked the financial means to keep Lavoisier's weather stations going, and was forced to rely on his own observations. Fortunately, he was an outstanding observer. At home in the
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plant and animal kingdoms like few others, he now directed his keen eyes towards the sky — ^not at the stars, which he left to better mathematicians, but at the clouds. While millions of people had done just that before him, and like Hamlet had been content to see that clouds looked now like camels, now like weasels and now like whales, ^ no one had ever thought of classifying clouds according to their shapes and other charac- teristics. This was to be Lamarck's achievement, for though it took meteorologists almost a hundred years to agree on an international system of cloud classification, it was Lamarck's language that they eventually employed — with modifications.
To keep track of his observations, Lamarck began to com- pile weather charts with the assistance of Laplace, one of the greatest mathematicians and astronomers of his day. These two men made a unique team. Lamarck, always concerned with con- crete facts, was convinced that all nature was purposive and that the art of living was the art of adaptation. Thus, in 1809, in his Philosophie Zoologique he put forward the thesis that nature improved the organisation of animals gradually, and that all animals were modified in form and habit by their environment. No wonder that he was so interested in climate and weather conditions.
Laplace, on the other hand, took a more exalted and abstract view of nature. For him, all research was the discovery of universally valid laws. He was the strictest determinist of all time, and it is he who coined a phrase that was to remain on the lips of scientists for a whole century: "A mind which, at a given moment, had full knowledge of all the forces vitalising nature, and of the position of all the beings of which nature is composed, and which would, moreover, be broad enough to submit these phenomena to analysis, would be able to apply one and the same formula to the motions of the celestial bodies and the lightest atoms alike. Nothing would be uncertain for such a mind, and past and future would be immediately present."
Though Laplace was fully aware that his ideal was unattain- able, he nevertheless suggested that it be used as a guiding principle in all research. It was with this aim in view that he developed his celestial mechanics, in which everything worked like a clock that needed no one to wind it up. Applying his ideas 1 Hamlet, Act III, Scene 2.
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to meteorology, he produced laws and calculations whose accuracy continues to astonish scientists to this day. The decrease of air pressure with increasing height^ — a phenomenon that had long been known to all mountaineers — was calculated precisely up to a height of 30,000 meters where, in fact, the stratosphere throws Laplace's calculations out of gear. It was his realism which persuaded meteorologists not to waste their time on idle speculation. His Annuaires meteorologiqms ( 1 800— 1812) were full of practical advice.
On the opposite side of the English Channel, as well, people had begun to take a keen interest in practical meteorological problems, particularly as they affected navigation. The weather in London or Manchester was no grave problem since, after all, most people could afford to carry umbrellas on their arms, but storms on the ocean wasted ships, lives, and a great deal of money. Though Parliament had repeatedly offered high rewards for discoveries and inventions that would contribute to the safety of ships and seamen, no one came forward with any practical means of predicting gales off the coast, let alone on the high sea. By the time Queen Victoria ascended the throne in 1837, this danger was no smaller than it had been 250 years earlier, when a storm, by destroying the Spanish Armada, made England the world's greatest maritime nation.
The debacle of Balaclava
The main trouble was the same on both sides of the Channel: ignorance of weather conditions in the rest of the world. By means of weather charts which were by then being drawn up in many parts of the world, a wealth of data had been accumulated, and it was known roughly how long it took for high pressure and low pressure areas to disperse, with what speed high winds travelled cross-country, and so on. But all this knowledge was useless for the simple reason that it could not be applied quickly enough. Even had the number of weather stations been increased tenfold, little advantage would have been gained, since the main fault lay in the slowness of communications. A whirlwind travels with an average speed of 30 m.p.h., i.e. four times as
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quickly as even the fastest coach, twice as quickly as the fastest dispatch rider. Even trains travelled much too slowly and too irregularly to carry news of storms before they broke.
This shortcoming was only remedied with the invention of the electric telegraph, or rather 15 years later when enough cables had been laid and enough equipment constructed. During the 19th century, sufficient progress had been made for every progressive town to have a telegraph office. Even then a major catastrophe was needed before governments realised the need for international exchanges of weather information.
On the 14th November 1854, during the Crimean War, French and British men o' war at anchor in the harbour of Balaclava were overcome by a sudden storm which endangered the success of the entire expedition. Paris was in an uproar, and in his desperation, the Minister of War, the Marechal Vaillant, instructed the famous astronomer Leverrier, whose calculations had led to the discovery of Neptune, to devise a means of avert- ing similar disasters in the future. Leverrier's considered reply was that he could only undertake that task if he could rely on a well organised network of weather stations, and the Marechal granted Leverrier's demand.
By making inquiries from various scientific institutes, Le- verrier managed to plot the route of the atmospheric disturbance that had led to the Balaclava disaster, and his map in itself was so convincing an argument, that even countries opposed to an international weather bureau, became converted. Observatories all over Europe began to wire daily weather reports to Paris and, in return, were warned by Paris of any storms moving in their direction. When Paris wired its first reports to the world at large on the 1st June 1860, the event marked a milestone in the history of scientific prediction.
An organisation had at last been set up that meteorologists had vainly tried to establish for generations. Oddly enough, this great advance did little to prevent meteorology from remaining stagnant for the next fifty years — it looked much the same in the early 20th century as Leverrier had left it in the middle of the 19th century.
Meteorologists will explain that this failure was the result of their art having fallen into the wrong hands, viz. into those of statisticians, instead of great mathematicians like Laplace. For a
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number of decades it was most fashionable for meteorological institutes, which had by then begun to lead a separate existence from astronomical observatories, to calculate nothing but averages. Average temperatures, average rainfall, average snowfall, average hours of sunshine, and so on, were recorded in every village worth its name, and favourable results were pasted up in large letters on all public places by way of advertisement. While this attracted holiday-makers, meteorology was becoming stifled by all these averages which had little predictive importance. 1
Still, this insistence on averages alone could not have been the main reason why meteorology failed so badly, at a time in which all other branches of applied science made such great strides. The real reason was probably that the public demand for weather forecasts had greatly fallen off. The 19th century was largely an urban age, people lived in strong stone houses with strong roofs that no storm could dislodge ; they dressed in protective clothes, and travelled by omnibus, tramway, or train which ran irrespective of weather conditions. Even ships had less to fear from the weather than before. In short, the weather had lost most of its threatening character, and was no longer worth bothering about a great deal.
fFar in the air
Things took a new turn with the advent of the aeroplane. Flying was not merely a triumph of mechanical genius and engineering know-how, but of meteorology, as well. Without prior research by meteorologists, the Wright brothers could never have hoped to keep their primitive equipment in the air for even a few minutes. Flying might have remained a mere sport, had not the First World War forced governments to call in their meteorologists.
The great meteorological contribution to aerial navigation was not made by any of the countries at war but by neutral Norway, where after years of careful observations, Vilhelm Bjerknes, a meteorologist attached to the Bergen Geophysical * Andr6 Viaut: La Mit^orologie (Paris 1954), p. 8.
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Institute, became convinced that there was something radically wrong with all previous methods of weather-forecasting. Now, since the first half of the 19th century meteorologists had mainly concentrated on the study of cyclones, by which experts mean a system of winds rotating around a centre of n^iinimum barometric pressure. Leverrier had made it a common dogma that all cyclones were dangerous, and his thesis seemed com- pletely corroborated when the Dutch meteorologist Buys- Ballot formulated his general laws of storms (the Ballot Laws). From then on, the prediction of storms seemed to be a matter of pure calculation.
The only fly in the ointment was that the calculations did not lead to particularly good forecasts, and it was for this reason that Bjerknes opposed the cyclone theory with an entirely new conception: the weather was decided, not by individual cyclones but by general movements of air, particularly from the poles. Vilhelm Bjerknes, and his son Jacob who formulated the new theory even more precisely,^ thought and wrote in the language of their time, i.e. in World War I jargon, and their scientific dicta read like so many military proclamations. The sky is in a state of war, in which huge armies of cold and warm air face each other in close battle formation to vanquish or to be van- quished, according to fixed strategic rules: if a cold front is brought to a halt by a warm front, rain is formed behind the former and if a warm front is halted by a cold front, rain forms ahead of the warm front. If equally matched fronts face each other, the outcome depends on their temperature differences. In all cases the fronts are accompanied by specific cloud forma- tions, so that their nature can be ascertained quite simply.
The Norwegian theory proved particularly useful for aerial navigation. Before take-off, all pilots are handed a weather chart on which the fronts they will meet are carefully recorded. Such weather charts are, moreover, not used by airmen alone, but have become one of the essential tools of all meteorologists. Thus the entire meteorological system of the United States was reorganised by Carl-Gustaf Rossby, one of Vilhelm Bjerknes's pupils, to conform with the Norwegian system, and even French meteorologists, who still base their predictions on the old cyclone
^ W. J. Humphreys: Ways of the Weather (Lancaster, Pennsylvania 1944), pp. 387-390.
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theory, have learnt to accept a great deal of the frontal theory, as well.
Naturally, theory is not the be all and end all of weather forecasting. Careful observations, accurate calculation, and an efficient system of international communications are as necessary today as ever they were. And communications continue to be the greatest bugbear, since as a result of bad international relations, meteorological co-operation has been steadily decreasing. Apparently the fronts of the Cold War are more intransigent than those of the atmosphere. Even so, regular weather reports are broadcast from eight centres: Arlington (U.S.A.), Rio de Janeiro, Rugby (England), Moscow, Vladivostok, Nairobi, Delhi, and Guam. Airmen, in particular, are well looked after, for more than 1200 meteorological forecasts are broadcast daily in international code.^ Shipping, too, is kept in touch with meteorological development by nine floating weather-stations and 22 weather ships. The Communist bloc does not participate in this maritime service.
Freddy, the frog
On the whole, weather predictions have improved by leaps and bounds, though, in some«respects, they have remained bogged down in uncertainty. Thus mountain-weather forecasts are still so unreliable that false forecasts often outnumber correct ones for weeks on end. According to the very reliable evidence of Councillor Robert Heindl, a leading Bavarian criminologist who lives just outside Munich and who made detailed records of rainfall, air temperature and hours of sunshine at 6 a.m., noon, and 6 p.m. from the 24th July to the 23rd August 1956, in order to compare his entries with the official weather forecasts for Southern Bavaria, not a single prediction was correct from 24th July-7th August. For the next two weeks, the Central German Meteorological Office predicted a persistent stable and dry spell, whereas Heindl noted rains, storms and even a mono- tonous drizzle. For three successive days, rain fell uninter-
^ Eugene Pepin: Ghgraphie de Id circulation aerienne (Paris 1956), p. 110.
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ruptedly. Our criminologist concluded from all this that his frog Freddy seemed a better judge of the weather than all the meteorological experts put together.^
Official weather forecasts like these remind us of Pico della Mirandola's predictions made 500 years earlier. While we hold no brief for frogs, let alone for astrologers, we cannot help marvelling why meteorology has failed to make sufficient pro- gress these last 500 years, to be able to predict mountain weather accurately for even the next 24 hours.
In lower altitudes, on the other hand, it is quite usual to find that 24-hour weather forecasts are correct over long periods, and that the general trend of the weather is rarely miscast. But even here, there are occasional errors in the time interval: a change in the weather predicted for the next day may only take place in two days, and vice versa. In Rio de Janeiro, where meteorologists are particularly brave and fly coloured weather flags from the tallest sky-scraper, people have often seen the white, good weather, flag being hauled in almost as soon as it was hoisted, and just before their city was turned into a second Venice by a tropical downpour. But then Rio de Janeiro has an exceptional position: not only does it lie on the sea, but it is surrounded by a chain of mountains.
Still, many false weather forecasts are less due to adverse geographical conditions, than to miscalculations. Weather forecasts are based on countless factors, some of which — e.g. temperature conditions — are so well-known that conclusions can be drawn from them directly or by simple calculation. Other factors, however, are so complicated that general weather pre- dictions always involve a large subjective element, and the day still seems far off when rules of thumb will enable every trained meteorologist to predict the weather purely mechanically. As it is, meteorology continues to be the application of known laws to more or less unknown events.
Doubling the scope
Large meteorological institutions with sufficient equipment 1 Suddeutscbe Zeitung (Munich), 30th August 1956,
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have more recently tried to extend weather forecasts not only in space but also in time. As late as 1920, no weather bureau would dare to make forecasts for more than 24 hours, and it was only in 1930 that the Meteorologie nationale in Paris, which did pioneer work in this field, began to make 36-hour forecasts. In 1939, forecasts were extended to 48 hours, and since 1949, Paris and many other centres habitually make forecasts for two to four days ahead, though those for the last two days are usually couched in general terms.
While it may be said that this increase in the scope of meteorology represents a considerable achievement, this achievement pales into insignificance when compared with the rate of development of other branches of technology. From this fact alone we can conclude that the obstacles which meteoro- logists still have to surmount in applying their theories to natural processes, remain enormous. Their achievements in the aero- nautical field are largely due to the fact that all forecasts are short-term: the weather charts for the guidance of pilots are compiled every three hours and all unforeseen changes are radioed out immediately. The faster an aeroplane, the simpler the task, particularly when there is a world-wide net of special radio stations. Moreover, radar nowadays enables aeroplanes to spot approaching storms and cyclones without outside assistance.
Compared with such short-range forecasts, our daily weather service must be considered a long-term forecast, and 48-hour forecasts as almost prophetic. In fact, 48 hours continues to be the upper limit of normal weather forecasts, since neither the Norwegian nor the cyclone theory can hope to make longer predictions, except under particularly favourable atmospheric conditions.
Such favourable conditions exist, for instance, when we know the velocity with which a "low" is travelling, in which case accurate forecasts for four or even five days can be made. Take the following actual forecast: "The atmospheric disturbance over the N. American Lakes at 1 p.m. on 12th January will have reached Newfoundland by 1 p.m. on the 13th January, and will have reached Europe via Ireland on the 15th, and via N. France early on the 17th January." To make this forecast, the weather staion in question knew no more than that an area of low pres-
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sure was travelling at about 36 m.p.h. eastwards along 50°N. Actually, such forecasts often go wrong, and even when the facts bear them out in detail, this is usually due to luck rather than to brilliant meteorological deductions.
Be that as it may, forecasts of the kind just mentioned are, in any case, within the technical scope of modern meteorology, whereas long term forecasts ( one to three months ) are not, since unlike short term forecasts, which are based on the analysis of concrete atmospheric phenomena, they are generally derived statistically, i.e. on the basis of past observations.
Geographically speaking, we know a number of centres of activity from which cyclones (depressions) and anticyclones (high pressure) take their origin. Anticyclones are usually formed in the Azores, the Bermuda Islands, Siberia, the central part of North America, while cyclones arise from Iceland and to a lesser extent from the Mediterranean. Now, we know that these regions are meteorologically related, i.e. high pressure in one will be accompanied by low pressure in another. Thus a depression between Iceland and Norway is usually accompanied by a high pressure area between the Azores and the Mediter- ranean, and if the winter is particularly severe in Northern Europe, it is usually very mild in North America and very cold in Mexico. But though theoretical considerations show that this compensatory process is somewhat similar to the simultaneous fluctuation of a liquid in the two arms of a U-tube, the pheno- mena are not quite simultaneous or not always equally strong. Thus Mexicans might be wrong to discard their heavy over- coats the moment they hear of a freeze-up in Canada.
Side by side with these more or less compensatory pheno- mena, meteorologists can also base their long term predictions on the occurrence of well-known sequences of events, most of which are still unexplained and simply taken for granted. One of the most curious of these is the relation between rainfall at distant points. Thus some meteorologists believe that there is a connection between the rainfall on the Faroe Islands and that on Berlin, the January-March rainfall in the former being a fairly accurate indication of the April-September downpour over the latter.^ Berliners would therefore do well to look to the Faroes when deciding on the purchase of rainwear. ^ Ren6 Valmar: Pour privoir le temps (Paris 1953), p. 151.
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Weather-lore
Although official weather prophets proclaim their opinions through wireless sets the world over, millions of people, most of them countryfolk, prefer to be their own weather prophets. Country weather-lore may differ from country to country, and from region to region, but it is always based on a mixture of ancient superstititions, relics of antiquated science, and very shrewd observation.
Countryfolk take their weather forecasts where they can. Their favourite assistants are birds, bats, flies, bees, spiders, worms, frogs, fish, cats, dogs, sheep, cattle — there is hardly a species of animal which does not serve the farmer as a weather prophet. And, in fact, animals do their job extremely well, for they are much more sensitive to weather changes than human beings. Certain animals are good-weather prophets, others are bad-weather prophets, and some combine both roles. Thus croaking frogs generally indicate good weather, unless they croak unusually loudly when a storm is to be expected. Bad weather is also imminent when toads and salamanders come out at night. Bees, on the other hand, retire to their hives before storms, and swarm in the early morning of bright days.
All these omens are usually short term warnings, for they occur only a few hours before the event. On the other hand, if cocks crow in the afternoon they are said to herald rain next day — a fairly long term prediction. But then cocks are so notori- ously unreliable that, according to an adage: "If the cock begins to crow, we may have sunshine, rain, or snow."
More reliable still than the behaviour of animals, is the behaviour of certain plants which react to moisture in the air. The most famous of these "hygrometric" plants is the Scarlet Pimpernel, which the botanist John Gerard called a weather prophet as early as 1597, and which closes when rainy or cloudy weather is imminent. Since Gerard's day, a host of such "weather flowers" has been discovered, quite apart from artificial "flowers" saturated with chemicals, e.g. cobalt chloride, whose colour changes with the humidity of the air.
A third, and probably the oldest type of "natural" weather prediction is based on the direction of the wind. Every peasant has some knowledge on this subject, but to master it he must