Thestarting point in any study of the physiological effects of weather and climate upon humanity is the remarkable fact that, on the hottest days of summer and the coldest of winter, in tropical deserts and amid polar snows, the temperature within the body of a healthy man remains constant to a fraction of a degree. There are slight temperature differences between different parts of the body; there is a periodic daily variation of about half a degree; and there are other slight changes, due to eating and exercise; but an internal temperature of about 98.6 degrees F. is maintained with little or no regard to fluctuations in the temperature of the air.
The body has often been compared to a building in which the temperature is regulated by a thermostat, but the comparison is not exact. The thermostat controls the temperature merely by regulating the combustion of fuel; and with the advent of mild weather we let the fires go out altogether. In the body the fires are always burning, the briskness with which they burn—or, to drop the metaphor, the rate at which bodily heat is generated—depending, above all, upon muscular activity, but also upon other causes. It is true that we possess a nervous mechanism, analogous to the thermostat,which tends to adjust the production of animal heat in such a manner as to offset the cooling effect of our environment; but this mechanism appears to be less important in maintaining our constant temperature than another, which regulates the loss of heat from the body. According to M. J. Rosenau:
“Heat is lost from the body chiefly in two ways; (1) byheat transfer, or loss by radiation, conduction, and convection; (2) byevaporation, chiefly by the evaporation of the water of perspiration. Pettenkofer and Voit estimated the loss of water by the lungs at 286 grams, and from the skin at from 500 to 1,700 grams daily. This will give some idea of the effects here concerned. The loss by heat transfer diminishes as the temperature of the surrounding air rises. The temperature of the body would rise when the atmospheric temperature goes above 70 degrees F. were not perspiration then secreted. So long as the perspiration can evaporate freely the heat production and heat loss are balanced. With a high humidity evaporation is lessened and the balance is maintained by rushing blood to the skin, which causes an elevation of the temperature of the surface, and thus the loss of heat by radiation, conduction, and convection is facilitated.”
Human sensations of temperature are paradoxical. We talk of being “hot” and “cold,” as if we belonged to the class of cold-blooded animals—the fishes and the reptiles—that actually undergo great variations of temperature, with variations in the temperature of their environment. We hear people say, for example, that they are most comfortable at a temperature of 65; yet we know that their temperature is always 98½, except just at the surface of the body.
The human body is, in fact, a poor thermometer. Our sensations do not register the temperature of the air, but they do, in a way, register the cooling power of the air, which depends upon temperature, humidity, and air movement, and they register, especially, changes in this cooling power, for within certain limits the body soon adapts itself to a constant rate of cooling, so as to lose any impression of heat or cold. When a steady outflow of heat from the body has been set up and the external cooling power is suddenly increased, we become conscious of a difference between the temperature at the surface of the body and the “blood temperature” beneath. The action of the nerves at the surface and the nerves underneath, under these circumstances, has been compared to that of a thermo-junction, in which an electric current is produced by differences of temperature. The rate of evaporation from the skin, also, has a marked effect upon our sensations of comfort and discomfort.
The common thermometer was long ago discredited as a means of measuring atmospheric comfort. Then, for a time, the wet-bulb thermometer had its day, and its indications were once published on a large scale in this country as representing the “sensible temperature,” or temperature that we actually feel. The wet-bulb thermometer is cooled by evaporation below the air temperature, except when the air is saturated with moisture, and may therefore give a rough indication of the temperature acquired by the skin when moistened with perspiration. The temperature of the skin is not, however, an accurate indication of our feelings of heat or cold, nor is it a satisfactory guide to the physiological effects of atmospheric conditions.
Several instruments have been devised for the purpose of measuring the cooling power of the air, to which the bodily mechanism must respond in order to maintain a uniform temperature within. One of these was invented nearly half a century ago by J. W. Osborne. A porous cylinder was filled with warm water, and an agitator, driven by clockwork, kept the water in the cylinder at uniform temperature at any given moment. The rate at which heat was lost from the wet surface of the cylinder was determined by a thermometer, having its bulb immersed in the water, and a stop watch. A different plan was adopted by A. Piche, in an instrument which he called thedeperditometer, and which was supposed to imitate more closely the behavior of the body. A porous vessel is filled with water, the temperature of which is kept constantly at “blood heat” (98.6 degrees F.) by a gas jet provided with an automatic regulator. The amount of gas burned in a given time is then supposed to measure the cooling power of the atmosphere as it affects humanity. J. R. Milne’spsuchrainometeris constructed on the same principle, but heat is supplied and measured electrically.
Among many other instruments of this class, one that now enjoys special favor is thekatathermometer, devised by Prof. Leonard Hill, in England. This consists of a pair of large-bulbed spirit thermometers, one of which has its bulb covered with fine cotton mesh. To use the instrument, the bulbs are immersed in water at about 150 degrees F. until the spirit rises to the top of the thermometer tubes. The excess of water is then jerked off the wet bulb, and the other bulb is dried. The instruments are finally suspended in the air, and the rate of coolingfrom 110 to 100 degrees, or from 100 to 90 degrees, is taken with a stop watch. The dry-bulb measurements are supposed to show how fast the human body loses heat at its surface by radiation and convection, while the wet-bulb measurements also take account of evaporation.
In order to connect the readings of this device with human sensations, Hill and his collaborators have used the instrument under a great variety of atmospheric conditions, both indoors and out, and compared the readings with independent estimates of comfort and discomfort. On an ideal summer day the “wet kata” fell from 110 to 100 in 25 seconds, and the “dry kata” in 85 seconds. Indoors at the seaside in summer, under comfortable conditions, the readings were 50 seconds and 140 seconds, respectively. A large number of other readings, taken under different conditions in various parts of the word, have been published. The katathermometer is now used in both Great Britain and the United States in the study of ventilation problems, and has acquired a rather extensive literature. According to its inventor, “the heating and ventilation of rooms should be arranged so that the wet-bulb falls from 100 to 90 degrees in about one minute, and the dry-bulb in about three minutes.”
A Weather Bureau Kiosk, in Union Square, San Francisco.(Photograph, U. S. Weather Bureau.)
A Weather Bureau Kiosk, in Union Square, San Francisco.(Photograph, U. S. Weather Bureau.)
A Weather Bureau Kiosk, in Union Square, San Francisco.(Photograph, U. S. Weather Bureau.)
The United States Weather Bureau Station, Observatory Type, at Peoria, Illinois.(Photograph, U. S. Weather Bureau.)
The United States Weather Bureau Station, Observatory Type, at Peoria, Illinois.(Photograph, U. S. Weather Bureau.)
Regardless of the merits of these particular instruments, it is certain that the cooling power of the air—which is quite a different thing from the temperature of the air—is a very important factor in determining our comfort and our health. Within certain limits the body can easily adjust itself to changes in the cooling power of the air; within wider limits the adjustment is effected with difficulty, and we experience discomfort and possiblysuffer in health; and finally there are extreme conditions, in either direction, to which adjustment is not possible; the internal temperature is then either lowered or raised, as the case may be, and a comparatively small change of this sort is fatal; i. e., death results by chilling or by heat stroke.
Photo U. S. Weather BureauTHE CENTRAL OFFICE OF THE UNITED STATES WEATHER BUREAU IN WASHINGTON
Photo U. S. Weather Bureau
THE CENTRAL OFFICE OF THE UNITED STATES WEATHER BUREAU IN WASHINGTON
One interesting result of recent inquiries on this subject is the discovery that the bad effects of crowded, “stuffy” rooms are not generally due to impurities in the air, but to heat, humidity, and especially lack of air movement. It seems to be now demonstrated that there is no such thing as “crowd-poisoning,” and that the bad smells of confined places are no indication that the air is deleterious. Professor Hill, who has done more than anybody else to upset traditional ideas with regard to ventilation, tells us that “the deaths in the Black Hole of Calcutta, the depression, headache, etc., experienced in close rooms are alike due to heat stagnation; the victims of the Black Hole died of heat stroke.” Most recent writers on physiology also discredit the time-honored methods of testing thepurity of the air by measuring the percentage of carbon dioxide it contains. The amount of this gas normally present in the free air is about three-hundredths of one per cent, but experiments have shown that thirty times this amount—a percentage higher than is found in the worst ventilated rooms—may be breathed for hours together without detrimental effects. A further departure from old-fashioned views is seen in the assertion of recent authorities that a deficiency of oxygen, unless far more pronounced than ever actually occurs in buildings, mines, etc., where the supply of this gas has been the subject of so much solicitude, has no physiological significance whatever. In support of this assertion it is pointed out that at mountain health resorts the concentration of oxygen out-of-doors is much less than that found in the worst ventilated rooms at sea-level. In mines an ample supply of oxygen may be positively dangerous, as favoring the occurrence of explosions. These were rare before the enactment of laws requiring a high percentage of oxygen in mine air.
HILL’S KATATHERMOMETER
HILL’S KATATHERMOMETER
Excessive dryness of the skin, which is a common cause of discomfort, is not very closely related to the humidity of the air. “In winter,” says Hill, “if there be a wind the rate of evaporation is so accelerated that the skin feels dry, because in order to check the loss of body heat the sweat glands are inactive and the blood vessels of the chilled skin are constricted.” There has been a great deal of discussion about the dry air of American buildings in winter, and startling figures have been adduced to show that the air of such buildings is dryer than that of deserts. So far as measurements of relative humidity go, this is perfectly true; but, as Dr.G. T. Palmer, of the New York State Commission on Ventilation, has pointed out, there is an important difference between dryness and “dryingness.” The latter depends upon the movement of the air, as well as the relative humidity. The circulation of the air in a desert is generally much more active than that of the air in a building with the windows shut, and therefore much more conducive to rapid evaporation. There are systems of ventilation in which the air is kept in steady and rapid motion, and it is probably only in such cases that the air of our heated houses can be compared to that of a desert. From the European point of view American buildings are notoriously overheated, but this is probably due to the fact that our hot summers—much hotter than those of Europe—have adapted us to a tropical climate.
It is natural to inquire whether the atmospheric conditions that affect the comfort of man do not also exercise a marked influence upon his muscular efficiency and his mental powers. This question has been answered in the affirmative by a number of ingenious writers, who have sought to establish definite quantitative relations between certain states of the atmosphere and the output of work in factories, the grades attained by school children, etc. Thus, Dr. Ellsworth Huntington, a well-known worker in this field, declares that the most favorable daily mean temperature for mental activity (the temperature being measured out-of-doors) is about 40 degrees F., and for physical activity about 60 degrees F. Contrary to the common opinion, he holds that our general efficiency is at low ebb in midwinter and fairly high in summer. Variability in temperature, within certain limits, he finds to bestimulating; equable temperature the reverse. He has drawn charts showing the distribution of what he calls “climatic energy”—i. e., the combination of certain weather factors supposed to control human efficiency—throughout the world, and other charts showing a more or less similar distribution of “civilization.” He has also made an ambitious attempt to interpret the history of mankind in terms of weather and climate.
Another fruitful worker along similar lines is Dr. Griffith Taylor, of Australia, who has made interesting studies of the control of settlement in his own country and elsewhere by temperature and humidity, and has introduced some novel graphic methods (“climographs”) for comparing climates with respect to their effects on humanity.
There has, in short, arisen a new school of climatologists whose aim is to develop exact mathematical formulæ whereby we shall be able to adjust the economic arrangements of mankind on an intelligent basis as regards climate. The success of their efforts is a question for the future to decide, but there is no doubt that their work is profoundly suggestive. These undertakings, it may be noted, bear a striking analogy to those of the present generation of agricultural meteorologists, who are applying climatic statistics to the problem of selecting crops and to the improvement of agricultural methods.
A certain number of specialists are engaged in studying the physiological effects of sunlight and other special kinds of solar radiation, the distribution of which varies greatly from place to place and from time to time, especially on account of differences in the selective absorption of such rays by the atmosphere. The chemical action of sunshine thatcauses sunburn—even at very low temperatures, as, for example, on high mountains—may have far-reaching effects on the human organism (as it certainly has on plants), and there is great need of collecting more data of “photochemical climate” than we now possess, in order that this subject may be thoroughly investigated. One of the few institutions in the world at which a large amount of work has been done in this line is the private observatory of Dr. C. Dorno, at Davos, the well-known health resort in the Alps. Dorno’s studies throw a good deal of light upon the therapeutic effects of sunshine in a mountain climate.
Many forms of dust in the atmosphere are capable of producing pronounced physiological and pathological effects. There is a long list of “dusty trades” in which the production of excessive dust has notoriously evil effects upon the health of workmen, leading especially to pulmonary diseases; sometimes to various kinds of poisoning. These harmful dusts are by no means confined to factories, mines, quarries, and the like. The air of the average city street abounds in them. Dr. J. G. Ogden states that 61 per cent of the dust found in the air of the New York subways consists of jagged splinters of steel, resulting from the wearing away of brake shoes, wheels, and rails.
The amount of danger to human health incurred through the presence of disease germs in the atmosphere has been the subject of much controversy. The present tendency is to regard this danger as very slight, under ordinary conditions. Thus, Dr. F. S. Lee writes:
“Evidence that disease germs pass through the air from room to room of a house or from a hospitalto its immediate surroundings always breaks down when examined critically. It is indeed not rare now to treat cases of different infectious diseases in the same hospital ward. The one place of possible danger is in the immediate vicinity of a person suffering from a disease affecting the air passages, the mouth, throat, or lungs, such as a ‘cold’ or tuberculosis. Such a person may give out the characteristic microbe for a distance of a few feet from his body, not in quiet expiration, for simple expired air is sterile, but attached to droplets that may be expelled in coughing, sneezing, or forcible speaking. In this manner infection may, and probably does, occur, the evidence being perhaps strongest in the case of tuberculosis. But apart from this source there appears to be little danger of contracting an infectious disease from germs that float in the air.”
In regard to sewer gas, which still inspires so much dread in the popular mind, Dr. Lee says:
“Workmen in sewers are notoriously strong, vigorous, healthy men, with a low death rate among them. The specter of an invisible monster entering our homes surreptitiously from our plumbing pipes and sapping our lives and the lives of our children must be laid aside; we need no longer leave saucers of so-called ‘chlorides’ standing about our floors to neutralize in an impossible manner mysterious effluvia that do not exist; and when we return to our town houses in the autumn we may enter them with no fears that we are risking our lives by coming into a toxic, germ-infected, sewer gas-laden, deadly atmosphere.”
Present-day knowledge on the subject of infectious diseases discredits many ideas that once prevailedwith regard to the effects of tropical climates on health. The remarkable results accomplished by vigorous sanitary measures in such places as Havana, the Isthmus of Panama and Guayaquil have aroused hopes—perhaps too sanguine—that eventually all parts of the tropics will be made healthful for the white race. In the Canal Zone the death rate of the large population of American men, women, and children is not higher than prevails in many cities of the United States; whereas, a generation ago, when the French were at work on the canal, the “climate” of this region was regarded as one of the most unhealthful in the world. Some authorities go so far as to assert that the deterioration in the general health and efficiency of white people in the tropics, so far as it actually occurs, is due entirely to preventable diseases. It would seem more rational, however, to assume that there are climates both in and out of the tropics which, on account of their heat, humidity, and other purely physical factors, are not so suitable for habitation for any race of humanity as others. How far acclimatization can go toward offsetting the effects of these atmospheric conditions is problematical.
The changes in the barometer that occur from day to day in regions where these changes are most pronounced are, on an average, not greater than those encountered in going from the bottom to the top of a good-sized hill, and are probably not directly of physiological importance. Certain European investigators, however, ascribe pathological effects to the minute and rapid barometric fluctuations—too small to be detected with an ordinary barometer—that occur, for example, when the foehn wind isblowing. Whether this is the cause, or a contributory cause, of “foehn-sickness,” of which one hears in Switzerland, is still uncertain.
The physiological effects of a rarefied atmosphere, as experienced in mountain climbing, ballooning, and aviation, are not yet well understood, despite the large amount of study that has been devoted to this subject. Recent views are thus summarized by Rosenau:
“The symptoms produced by a marked diminution in atmospheric pressure vary with circumstances. The effects are increased by cold, active muscular exertion, or improper clothing. The noticeable symptoms are increased rapidity of respiration and acceleration of the circulation, noises in the head and dizziness, impairment of the senses of sight, hearing, and touch, dullness of the intellectual faculties, and a strong desire to sleep. Sudden changes to a rarefied atmosphere cause syncope, weakness, dyspnœa, dizziness, and nausea. These threatening symptoms go by the name of ‘mountain sickness,’ Bert and Journet believe this condition is due to lack of oxygen, and the symptoms may, in fact, be relieved by adding oxygen to the air inspired. Kronecker concludes that mountain sickness is caused by a congestion of the lungs, impeding the flow of blood through them. Mosso and his followers attribute the physical disturbances of a reduced atmospheric pressure to the fact that the blood loses carbon dioxide more quickly than it loses oxygen, and they ascribe mountain sickness to this decrease of carbon dioxide in the blood. Cohnheim believes there is a concentration of the blood at high altitudes; in fact, insignificant increases have been found by competent observers.”
Divers and workers in caissons are subjected to high barometric pressure, amounting, at the maximum, to about 4½ atmospheres. According to Rosenau:
“The physiological effects of an increased atmospheric pressure are mainly due to an increase in the amount of atmospheric gases (especially nitrogen) which are taken up by the blood, and also to an increase in the chemical absorption of oxygen by the blood. The serious consequences usually result from too rapid decompression. As the pressure is released gas bubbles form. Gradual decompression gives a chance for the gas to escape from the lungs and be expelled without the production of bubbles.”
The health and comfort of many people seem to be affected, in a rather striking way, by the passage of the barometric depressions and areas of high pressure that alternate at intervals of a few days in the temperate zones. These effects should not be ascribed to changes of pressure, but rather to the accompanying changes in the other meteorological conditions. The late Dr. Weir Mitchell, who was a pioneer student of such phenomena, wrote of “a neuralgic belt, within which, as it sweeps along in advance of the storm, prevail in the hurt and maimed limbs of men, in the tender nerves and rheumatic joints, renewed torments called into existence by the stir and perturbation of the elements.” Victims of neuralgia and rheumatism are probably quite justified in regarding themselves as human barometers, capable of predicting with considerable accuracy the advent of stormy and rainy weather.
The fluctuations of temperature, humidity, and wind that attend the passage of barometric highsand lows would seem, in virtue of their effects on the heat-regulating mechanism of the body and consequent reactions upon the nervous system in general, to supply an ample explanation of the unpleasant symptoms above noted in the case of sensitive people; conditions to which the collective name of “cyclonopathy” has been given by European investigators, and which are extensively discussed in the works of Hellpach, Frankenhäuser, and Berliner. Some authorities have, however, invoked in this connection the possible effects of atmospheric electricity, and pointed to the extreme sensitiveness of many persons to the approach of thunderstorms; a condition which Dr. G. M. Beard named “astraphobia.” It is stated that the passage of a low-pressure area favors the emission of radioactive emanations from the ground, that the ionization of the atmosphere, and hence its electrical conductivity, is thus increased, and that the electric charge of the body is carried away more rapidly than usual. Here we enter upon a debatable subject, but one that thoroughly merits investigation. The human organism is the seat of various electrical phenomena, and these certainly cannot be independent of changes in the electrical state of the atmosphere.
Apart from possible direct effects of atmospheric electricity upon the human system, it has been suggested that electrical changes in the atmosphere affect the rate of reproduction of bacteria, and may therefore have some influence on the spread of infectious diseases.
The weather has many subtle influences upon the human mind, producing moods of cheerfulness and depression, and manifesting themselves in the recordsof the behavior of school children, in statistics of crime, insanity, suicide, drunkenness, etc. An interesting account of these manifestations is given by Dr. E. G. Dexter in his book “Weather Influences” (New York, 1904).
Finally, the aspect of meteorology that has thus far acquired the most definite shape in medical circles and given rise to the most coherent body of literature is Medical Climatology, which is designed to be applied in the climatic treatment of disease (climatotherapy). Thus many compilations have been made of the climatic statistics of health resorts, and these resorts have been classified with respect to their supposed climatic effects upon various diseases. From the point of view of the physical climatologist, the statistics found in such books seem, in general, both meager and ill adapted to bring out important features of the climates discussed; to say nothing of the fact that the whole subject of climatotherapy is fraught with controversy—whereof the history of the treatment of tuberculosis furnishes a shining example!
Meteorologists,in their candid moments, have been heard to express disappointment over the amount of progress made in the art of weather forecasting during the past half-century. “Shall we ever,” they ask, “be able to predict the weather with mathematical certainty, as the astronomer predicts an eclipse of the sun or moon?”
Perhaps even within the meteorological fold there are unorthodox optimists who would answer such a question thus: “Yes, because some day we shallcontrolthe weather. It is inconceivable that man, who is every day achieving new miracles in the conquest of nature, should not eventually find a way of regulating the rainfall and sunshine that are of such vital importance to his crops, the winds that must be reckoned with in his voyages by sea and air, and the various other elements of weather that have so much to do with his happiness and welfare. The attainment of this object is so tremendously desirable that it cannot forever baffle human ingenuity.”
In support of such a bold assertion it might be pointed out that we already control the weather to a certain limited extent. When the horticulturist burns orchard heaters to protect his fruit from frost he certainly alters the weather for a few hours over a small area of the earth. If there were any practical justification of the process, the temperature ofthe air over an entire State, for example, could be raised throughout the winter, with appreciable effects on agriculture. The difference between heating a single orchard for a night and heating a State for a season is one of degree, and not of principle.
The climate of a city is, through causes dependent upon man, materially different from the natural climate of the surrounding country. Every dwelling provided with heating arrangements enjoys an artificial summer amid the blasts of winter. Local control of the winds is exemplified in the planting of thousands of miles of trees as windbreaks in the prairie regions of our Middle West. By moderating the winds this process has a marked effect on temperature and evaporation and is so beneficial to crops that in the aggregate it furnishes a striking example of successful “weather-making” by mankind. Analogous methods, perfectly feasible with means already at our disposal, would change the whole climatic aspect of large areas of the earth’s surface.
The question “Can we make it rain?” may be answered in the affirmative by those who are neither impostors nor victims of self-delusion. The deposit of spray from the spout of a teakettle might, without much stretching of terms, be described as a miniature artificial rainstorm; but much bigger showers, in nowise different from those occurring in nature, can also be produced artificially. Huge clouds have often been observed to form over forest fires and other great conflagrations. These clouds, composed of water drops, tower far above the smoke cloud, and are identical in character and mode of origin with the cumulus and cumulo-nimbus clouds formed by currents of moist air rising from the heated ground on a summer day. There are several well-authenticated cases in which rain has been seen to fall from such clouds, and these showers have sometimes been so heavy as to extinguish the fires that generated them. Hence, given favorable conditions of humidity, temperature and wind, mankind can certainly produce a rainstorm (and perhaps a thunderstorm into the bargain) by the relatively simple process of building a big fire.
Unfortunately the vast majority of methods whereby man has attempted to regulate the weather have no such rational foundation as those we have just mentioned. Some are wholly superstitious, others are purely empirical, and yet others are based upon ideas that their promoters suppose or pretend to be scientific, but that are actually fallacious.
In the history of superstitious practices weather-making plays a prominent part. Sir J. G. Frazer, in that great storehouse of myth and folklore, “The Golden Bough,” says: “Of the things which the public magician sets himself to do for the good of the tribe, one of the chief is to control the weather and especially to insure an adequate fall of rain. In savage communities the rain-maker is a very important personage; and often a special class of magicians exists for the purpose of regulating the heavenly water supply.” Frazer devotes ninety pages of his work to a rapid survey of the superstitious methods of controlling the weather that have found credence among the various races of mankind. These range all the way from the most complicated ceremonies to the summary expedient of throwing a passing stranger into a river to bring rain.
The sailor who whistles or scratches the mast to raise a wind is merely keeping up a quaint custom,in the efficacy of which he may or may not put some lingering faith, but which the world at large long since ceased to take seriously. When, however, a vessel master attempts to disperse a waterspout by firing a cannon at it, he is doing what nine educated persons out of ten would probably do under the circumstances. Yet one process is no more futile than the other, and both are based on superstition. Ages ago sailors sought to frighten waterspouts away by pointing knives at them, or by shouts and the clashing of swords, and the use of cannon originally embodied the same idea of terrifying the watery monster. It is our purpose in the present chapter to describe especially several processes of weather-making which, while not obviously chimerical from the point of view of the layman, have been more or less positively discredited through the scrutiny of men of science.
The efforts of modern weather-makers have been directed especially to two objects; viz., the production of rain and the prevention of hailstorms. In the United States a certain amount of ingenuity has also been devoted to the task of dispelling tornadoes. Some years ago a device for the latter purpose was patented, consisting of a box, containing explosives, mounted on a pole and erected a mile or so to the southwestward of the village to be protected from these unwelcome visitors. The force of the wind was expected to detonate the explosives by driving a movable board against percussion caps. The inventor believed that a violent explosion would disperse the passing tornado funnel. Apart from the fact that a single installation of this character, or even several of them, would seldom happen to be at exactly the right spot to explode close to the relativelysmall vortex of a tornado, the effect of the explosion, even in the very heart of the storm, would certainly be negligible. The energy that keeps the tornado in action is supplied continuously from a level far above the earth, while the disturbance due to the explosion would be only momentary. Above all, the energy developed in any discharge of explosives that the community could afford to pay for would be quite insignificant compared with that which prodigal nature supplies to the tornado.
The same disproportion between the giant forces at work in the atmosphere and the pygmy forces at the disposal of mankind is a point that is overlooked in most attempts at weather-making.
The widespread belief that rain can be produced by explosions rises so far above the level of ordinary popular delusions that it has sometimes led to large expenditures of money on the part of drought-ridden communities and even of national governments. Perhaps the most remarkable example of official confidence in the efficacy of this process was that furnished some years ago by the Volksraad, or legislative assembly, of the Transvaal, which passed a law forbidding the bombardment of the clouds to produce rain, on the ground that the rain-makers were thwarting the will of the Almighty!
One manifestation of the belief in question is found in the common assertion that rain is the usual sequel of battles. This idea originated, however, long before the invention of gunpowder. It is mentioned by Plutarch and other writers of antiquity. Whatever superstition or crude process of reasoning may have first given support to this notion in the popular mind, the explanation now commonly advanced is that the condensation ofmoisture is promoted by the concussion due to cannonading, or that the drops already condensed and constituting the clouds are jostled together by the same disturbance, with the result that they coalesce and fall as rain. There is no ground for such assumptions. As was once pointed out by the late Professor Simon Newcomb, the effect of a violent explosion upon a body of moist air a quarter of a mile distant is about the same as that which the clapping of one’s hands would produce upon the moist air of the room in which the experiment is performed. Again, if we stand in the steam escaping from a teakettle and clap our hands we shall not produce a shower, though we jostle the water drops much more than the explosion does at a distance of a quarter of a mile.
In recent years another explanation has been offered for the alleged production of rain by explosions; viz., that the smoke and gases arising from an explosion increase condensation by increasing the number of “nuclei” in the atmosphere. As we have seen, however, in considering the natural formation of rain, the number of condensation nuclei normally present in the atmosphere is so great that it must be diminished, rather than increased, before drops as large as raindrops can be formed. Moreover, the nuclei required for the condensation of water vapor, including molecules of highly hygroscopic gases, are given forth in abundance by great manufacturing centers, yet these places do not have a heavier rainfall than the surrounding country. Pittsburgh, for example, is actually one of the driest places in Pennsylvania.
One obvious reason why rain often follows a battle is that battles are frequently fought in regionswhere rain normally occurs every two or three days, on an average, whether in peace or war. In northern France, for example, where the battles of the World War were plenteously interspersed with showers, meteorological records show that the average number of rainy days per annum is upward of 150. The drenching rains that made “Virginia mud” a byword during the American Civil War gave great currency to the belief in “rain after battles,” Here, again, we have accurate weather records to help us dispel a fallacy. Thus at Richmond rain falls on 122 days in an average year, at Lynchburg on 124 days, and at Petersburg on 105 days.
There is, however, a particular reason why rain is rather more likely to occur soon after a battle than shortly before one; viz., the fact that intervals of fair weather, with consequent dry roads, are used by commanders in carrying out the movement of troops that precede an engagement. By the time such arrangements, often occupying several days, are completed, the “spell” of fine weather is likely to be over, and a rainstorm is due in accordance with the normal program of nature.
The most famous undertaking in the history of rain-making—and one which has had an incalculable effect in fostering the credulity of the public with respect to similar enterprises—was that carried out by General Robert Dyrenforth on behalf of the United States Government in 1891. Congress voted appropriations amounting to $9,000 for these experiments, and Dyrenforth was appointed a “special agent” of the Department of Agriculture to direct them. After some preliminary trials in the suburbs of Washington, the experimenters proceeded to a ranch near Midland, Texas. Here a few balloonsfilled with a mixture of oxygen and hydrogen, as well as several sticks of dynamite carried up by kites, were exploded in the air, but the only explosions of considerable magnitude were set off on the ground. The experiments continued over a period of three weeks and in some cases showers fell within a few hours after an explosion, but, in spite of the somewhat favorable tone of the official report, the consensus of scientific opinion was that the undertaking was a failure, while the views of the public at large were divided. The attitude of the Government is sufficiently indicated by the fact that it has never since undertaken experiments in this line. The one tangible outcome of this affair was that a crop of private rain-makers sprang up all over the country, and to this day the example set by the official experimenters is cited in support of every sort of harebrained scheme for juggling with the weather.
In 1911 and 1912 the late C. W. Post, of breakfast-food fame, expended many thousand pounds of dynamite in efforts to produce rain in Texas and Michigan. Showers undoubtedly occurred in conjunction with Post’s experiments, but conditions favoring their occurrence were plainly indicated on the current daily weather maps, and they had been duly forecast by the Weather Bureau.
The professional rain-maker does not generally resort to the expensive process of bombarding the clouds. His methods most frequently involve the use of chemicals, and the details are shrouded in mystery. For example, about a quarter of a century ago one Frank Melbourne, known as “the Australian rain-maker,” enjoyed great celebrity and coined money by his exploits in this field. His plan was to shut himself up in a barn, freight car, orother structure, and manipulate his chemicals and electric batteries for hours or days. Naturally rain sometimes came after these operations, but as often it did not.
Several of the methods that have been suggested from time to time for producing rain are sufficiently discredited by the fact that the expense of putting them into execution would more than offset any benefits derived from the rain, if the experiments proved successful. Thus one genius, observing the deposit of water on the outside of an ice pitcher in a warm room, proposed to set up a barrier packed with ice in the path of moisture-bearing winds. Another plan occasionally suggested is to sprinkle the atmosphere aloft with liquid air or liquid carbon dioxide, in order to lower the temperature, by the rapid evaporation of these substances, below the point of condensation. A third proposal is to create a local updraft of air by means of powerful fans or blowers, thus imitating the convectional process by which clouds and rain are formed in nature.
Lastly, various plans have been suggested for altering the electrical condition of the upper atmosphere—for example, by electrical discharges from balloons—on the assumption that rainfall might thus be promoted. This assumption, however, is not consistent with known facts as to the relation between atmospheric electricity and the condensation of atmospheric water vapor.
While in America a vast amount of money has been wasted on futile experiments in rain-making, far more has been spent in Europe on schemes for averting hailstorms. Methods of accomplishing this purpose have varied from age to age. In antiquity it was the custom to shoot arrows or hurl javelinstoward the gathering clouds in the hope of frightening them away. In the Middle Ages ecclesiastical or occult agencies were invoked; “hail crosses” (such as are still seen in the Tyrol) were erected; and the ringing of church bells was considered efficacious against both hail and lightning, as is shown by the inscriptions found on many old bells.
The custom of firing cannon at the clouds to avert hail began centuries ago in Styria and northern Italy, and it was well established in France before the Revolution. Toward the end of the eighteenth century, however, another method of hail protection was introduced in France, whence it spread over the rest of Europe. This consisted in setting up tall, metal-tipped poles, imitated from lightning rods. It was supposed that these poles, which were known asparagrêles, would draw the electric charge from the clouds and thereby (though nobody could say why) would prevent the formation of hailstones. This device, though reported on unfavorably by the French Academy of Sciences, gained great popularity. One of its advocates, writing in 1827, states that more than a millionparagrêleswere at that time in use in France, Switzerland, Italy, Austria, Bavaria, and the Rhine country. The vogue enjoyed by these contrivances is said to have come to a sudden end when a tremendous hailstorm not only devastated the fields and vineyards they were supposed to protect, but also knocked down a great number of the rods themselves.
In recent times both the hail cannon and theparagrêlehave been revived. The new era of “hail-shooting,” as the process of cannonading the hail clouds is called, dates from the year 1896, when a number of cannon of a new type were installed inthe vine-growing district of Windisch-Feistritz, in Styria. The success claimed for them in this region led to their introduction on a vast scale over the greater part of southern and central Europe. The cannon employed were small mortars, to the muzzles of which were attached sheet-iron funnels. No projectile was used, but the explosion of the charge sent aloft a curious whirling ring of smoke and gas, powerful enough to splinter sticks and kill small birds several hundred feet from the cannon. By the year 1900 at least 10,000 hail cannon were in use in Italy alone. Several modifications of the device were introduced, such as the use of acetylene in place of gunpowder; and eventually certain forms of rocket and bomb were adopted, for concentrating the effects of the explosion at as high a level as possible.
About the year 1899 a new form of hail rod was introduced in France, and this has become the favorite means of protection against hail in that country. It is essentially a very large lightning rod of pure copper, grounded by means of a broad copper conductor. Such rods have been installed, in some cases, on church steeples and other tall edifices, including the Eiffel Tower, in Paris, and in other cases on tall steel towers erected for this purpose. This device is called fantastically an “electric Niagara,” because, according to the claims of its promoters, it draws down “torrents” of electricity from the clouds. Hundreds of these “Niagaras” have been constructed in France. Some of them are set up in rows, or so-calledbarrages, across the habitual paths of hailstorms. The French Government was induced to appoint a“Comité de Défense contre la Grêle” (Hail-protection Committee), which beforethe war had made elaborate plans for “protecting” not only the whole of France, but also Algeria and Tunis, with these devices. Similar rods have been erected in Argentina, and plans for introducing them in South Africa were near consummation at the time the World War broke out.
In order to understand the extraordinary hold that the various hail-protecting devices have taken upon the minds of European cultivators it should be remembered that the intensive cultivation of the soil is the rule over the greater part of Europe, so that a hailstorm of relatively small extent often does enormous damage. Vineyards are especially subject to injury from this cause, and many of the richest vine-growing districts of the Old World are notoriously afflicted with hailstorms.
Scientific commissions appointed by the Austrian and Italian governments conducted long series of tests of the methods of bombarding the clouds with mortars, bombs, and rockets, and declared them to be of no value. The erection of hail rods, though it has received a certain amount of official encouragement in France, is also strongly discountenanced by the majority of scientific men, as well as by a large proportion of intelligent agriculturists. Reports on the actual operation of the rods support conflicting opinions—as might be expected from the fact that the hailstorm is a decidedly erratic phenomenon. Thus, some observers claim that the storm clouds change conspicuously in appearance as they approach a “Niagara,” and if they shed hail upon the spot it is in a soft and harmless form. Others deny the accuracy of these observations, and point to the stubborn fact that ordinary hail has fallen on several of the rods themselves, including the one on theEiffel Tower. In the suburbs of Clermont-Ferrand a “Niagara” is installed on an iron tower, 100 feet high. This rod was pelted with hail twice in 1912 and four times in 1913, and in one case the hailstones attained the size of hen’s eggs! Nobody has ever offered any plausible scientific hypothesis to explain why these rods should have an effect upon hail, even if they are able, as seems unlikely, to reduce the electrical charge of the clouds; since the formation of hail is due to movements of the air, which, in turn, are the cause and not the result of the charge in question.
Fortunately for the farmer and the horticulturist—especially in Europe—a method of averting the losses due to hailstorms is available in the shape of insurance, and its cost is decidedly less than that entailed in systematic hail-shooting or in the general erection of hail rods. Hailstorm insurance has been extensively practiced in the Old World since the end of the eighteenth century. In some countries it has been conducted or subsidized by the government. Generally each country is divided into a number of zones, according to the recorded frequency of hailstorms, and the premiums vary proportionately. Premiums also vary for different crops, since some are better able to withstand the effects of hail than others. The amount of insurance of this kind carried in Germany, alone, shortly before the World War, was more than $800,000,000.
Hailstorm insurance is fairly common in the United States, especially in the Middle West, but still lacks an adequate statistical basis in the shape of detailed records of hail frequency. In 1919 growing crops in this country were insured against hail to the extent of $559,134,000. Much informationon this subject will be found in V. N. Valgren’s “Hail Insurance on Farm Crops in the United States” (U. S. Dept. of Agriculture, Bulletin 912), published in 1920.
Besides the weather-making schemes already noted, mention should be made of certain more ambitious projects of this character that have been bruited from time to time, and that have found plenty of credulous supporters. In the year 1845 an American meteorologist of undoubted ability, but much inclined to the riding of hobbies—viz., James P. Espy—proposed the building of great fires in the western part of the United States in order to regulate the winds and rainfall to the eastward. The fires were to extend in a line of six or seven hundred miles from north to south, and were to be set off once a week throughout the summer. Another genius, of less celebrity, proposed to destroy blizzards by means of a line of coal stoves along the northern boundary of the country. A favorite idea of those who aspire to produce wholesale changes of climate is to alter the course of ocean currents for this purpose. One early plan contemplated the damming of the Strait of Belle Isle in order to improve the climate of New England and the Canadian provinces; while, a few years since, a proposal to build an immense jetty eastward from Newfoundland for the purpose of “protecting the warm north-flowing Gulf Stream from the onslaughts of the ice-cold, south-flowing Labrador Current” actually received, serious attention from the Congress of the United States.
Will-o’-the-wispis proverbially elusive. It has thus far escaped the fate of the rainbow, deplored by Keats. We do not know its woof and texture, and it is not given in the dull catalogue of common things.
A strong argument in favor of the reality of this phenomenon is found in the great number of names that have been applied to it. There are forty or fifty in the British dialects alone. A myth generally carries its nomenclature with it, as it spreads from one community to another, while a fact of nature may give rise to a variety of local names.
It is certain, however, that a great many different phenomena have been described as will-o’-the-wisp. Some of these are: (1) The phosphorescence of decaying wood (“fox fire”) and other vegetable matter. This is due to luminous fungi. According to H. Molisch there are some forty-five species of fungi, including twenty species of bacteria, that have the property of luminosity. Sometimes the ground under a forest is illuminated on all sides with a soft, white light from decaying leaves. (2) Fireflies, including glowworms (the wingless females of the firefly and the larvæ). (3) Luminous birds and animals. Their luminosity is supposed to be due to parasitic fungi. Certainspecies of skunk have been described as giving off in the darkness a continuous flame, the head being fiery red, which blends into a bright blue at the tail. (4) Ball lightning. (5) St. Elmo’s fire. (6) Moving lanterns, distant lights of houses, and other lights due to human agency. (7) Burning gas ascending from marshes, stagnant pools, and the like. Marsh gas and other inflammable gases commonly rise from such places, and are often ignited by man, or by lightning, etc. Such fires are sometimes seen by day as well as by night. (8) Burning naphtha springs.
Excluding the numerous reported cases of will-o’-the-wisp in which the phenomenon may be plausibly identified with one of those mentioned above, there remain several cases, some of them reported by very careful observers, which appear to belong to a different category. The reports in question differ somewhat in details, but yield the following composite description:
Small luminous bodies, “about as large as your fist,” or “the size of a candle flame,” are seen hovering a few feet above the ground; not only over marshes and pools, but also over dry land. Sometimes they are stationary; at other times they appear to drift with the wind, or even to move independently. They appear and disappear, after the manner of fireflies. They do not set fire to objects with which they come in contact, and are believed to be without sensible heat. Their color is most often described as bluish, but may be yellow, purple, green, etc.; rarely pure white. They are without odor and without smoke. Traditionally they are associated with graveyards, but in very few of the cases heretofore recordedwere they actually seen in such places. The popular idea that they flee from the traveler who tries to approach them and follow him when he seeks to avoid them is also unsupported by the evidence thus far adduced.
One of the most circumstantial accounts of these objects is that published in the Belgian journal “Ciel et Terre” for July-August, 1920, by a retired army surgeon, Jules Rossignol, who observed them repeatedly in the autumn of 1908 in and about some marshy woods near Grupont. They were generally seen to rise from the ground, at first in the shape of little white clouds, which changed to luminous globes on attaining an altitude of a dozen yards, and returned by a circular path toward the ground. They lasted from one to several minutes before disappearing in the air.
It is astonishing that the phenomenon ofignis fatuus, though reported from so many parts of the world, has not yet been made the subject of direct scientific examination. Nobody has ever studied its light with the spectroscope, for example. Chemists have, indeed, attempted to reproduce the phenomenon, yet the chemical explanations of it that have appeared in reference books down to a recent date are quite untenable. It has sometimes been attributed to marsh gas (methane, CH4), and sometimes to phosphureted hydrogen (phosphine, PH3). But marsh gas, besides not being spontaneously combustible, diffuses too rapidly in the air to produce the effects described, while phosphureted hydrogen, though it takes fire spontaneously in the air, produces thick wreaths of smoke when burning and has a powerful odor—features never reported in connection with will-o’-the-wisp.
At least two more plausible explanations ofignis fatuushave been offered in the last few years. Mr. F. Sanford (“Scientific Monthly,” Oct., 1919) believes that it is due to “swarms of luminous bacteria which are carried up from the bottom of the marsh by rising bubbles of gas.” A Belgian chemist, M. Léon Dumas (“La Nature,” Dec. 11, 1909), claims to have produced little luminous clouds, corresponding to the traditional descriptions of will-o’-the-wisp, by combining the two gases sulphureted hydrogen and phosphine. Both these substances are produced in the decay of animal matter, especially of the brain and spinal cord. The body of an animal, buried in some wet place, would accumulate the two gases under pressure in the skull and spinal canal, and their escape, simultaneously, would fulfill the conditions of M. Dumas’ experiments.
(At the request of the present writer, these experiments were repeated at the Bureau of Standards, in Washington, with only partial success. Further trials with these and other gases due to putrefaction are desirable.)
From time to time the newspapers publish accounts of a wonderful tree, said to grow wild in Peru or elsewhere, from the leaves of which falls a continuous shower of rain, even in the driest weather. The writers generally urge the introduction of this tree in regions where the rainfall is deficient, and a so-called “rain tree” has actually been sold for this purpose by nurserymen.
The story of this tree is very old. Early voyagers reported finding it in the East Indies, Guinea, Brazil, and especially the island of Ferro, in theCanaries. Nowadays the name “rain tree” is applied especially to a magnificent tree of tropical America generally known to botanists asPithecolobium(orEnterolobium)saman. One of its common names is “guango.”