CHAPTER V
WEATHER AND WEATHER INSTRUMENTS
The fact that a vast proportion of the conversations in which human beings engage begin with remarks about the weather has often been noted, but perhaps never fully explained. Meteorologists sometimes adduce this fact as evidence that weather is a subject of overshadowing importance. This bit of reasoning will not, however, bear critical analysis. It carries with it the implication that people talk about weather because weather is uppermost in their thoughts. How often is such the case? Brown, meeting Jones, remarks that it is a fine day. Are we to infer that Brown was meditating upon the agreeable state of the atmosphere before he vouchsafed this not altogether novel observation? Hardly. There is about one chance in a thousand that weather was in his mind at all.
It is a plausible thesis that people talk so much about weather because, at an earlier period in the history of mankind, this subject was of supreme importance. Perhaps it is a custom handed down from our remote ancestors, whose occupations were nearly all carried on out-of-doors and who enjoyed but a precarious shelter from the elements in their rude habitations. In India, as the period of the monsoon rains approaches, anxiety about the timely arrival and the abundance of these showers eclipses all other thoughts in the mind of the peasant, because a severe drought at this season means a famine. When our forefathers lived by hunting, fishing, and crude systems of grazing and agriculture, they were, no doubt, equally solicitous about atmospheric conditions that directly affected their food supply. In those days comments on the weather were by no means empty formulas. Men rejoiced together that the day was fine, because it was a circumstance upon which their dinner depended; and the prehistoric equivalent of “What beastly weather!” was probably accompanied by a significant tightening of the belt.
Certain it is that in very early times people gave a great deal of attention to the weather and acquired a fund of wisdom on the subject which, along with a certain amount of superstitious unwisdom, has come down to us in the shape of weather proverbs. Many of these proverbs undoubtedly originated before the dawn of history, for they are found in substantially the same form among widely scattered races of mankind. Various popular weather prognostics familiar at the present day are mentioned in such ancient documents as the Vedas, the Bible, and the cuneiform tablets from the library of Assurbanipal.
Speculations about the weather occupy much space in the writings of the Greek philosophers, and a formal treatise on meteorology, written by Aristotle (fourth century B. C.), remained the standard work on this subject for two thousand years. More or less systematic weather records were kept by the Greeks long before the Christian era, and they produced a number of almanacs, in the shape of marble tablets, showing the average winds and weather for particular dates throughout the year. A copious collection of the weather indications found in both Greek and Roman almanacs, dating back to the fifth century B. C., has been made by Dr. Gustav Hellmann.
Some of the meteorological instruments used today have a very respectable antiquity. Ancient statistics of the rainfall of India, recently brought to light, show that some sort of rain gauge must have been in use in that country in the fourth century before our era. Measurements of rainfall were made in Palestine in the first century A. D. The only other meteorological instrument dating back to classical antiquity, so far as known, is the weather vane. The Tower of the Winds, at Athens, built about a century before the Christian era, originally bore at its summit a vane in the shape of a bronze Triton, holding in his hand a wand, which was designed to point at one or another of the eight symbolical figures of the principal winds surrounding the octagonal tower, thus showing which way the wind was blowing at the time. The Roman writer Varro has left us a description of a vane that could be read indoors by means of a dial on the ceiling.
Instrumental weather observations did not become the rule, however, until the end of the seventeenth century, when the use of thermometers, hygrometers, barometers, and rain gauges began in Italy and spread rapidly to other countries. The origin of each of these instruments is commonly ascribed to a particular inventor—the thermometer to Galileo, the barometer to Torricelli, etc.—but the truth is that the idea of the instrument was, in each case, a slow growth, to which many minds contributed. Thus a form of thermoscope—a device for showing but not for measuring the expansion and contraction of air with changes of temperature—was described by Philo of Byzantium in the third century B. C. Galileo supplied such an instrument with a scale, but without fixed points, thus converting it into a crude thermometer, but it was not until half a century later that the Grand Duke Ferdinand II of Tuscany introduced the idea of filling the thermometer with alcohol, in place of air, and sealing it so that it was not affected by changes in barometric pressure. The thermometric scale now used in English-speaking countries, which bears the name of Fahrenheit, appears to have been devised by the Danish astronomer Ole Römer, from whom Fahrenheit borrowed it. In short, any brief account of the invention of the principal meteorological instruments necessarily ignores the just claims of many inventors; to say nothing of the fact that what is written on the subject to-day is likely to be refuted to-morrow by the discovery of some forgotten book or manuscript.
We are on safer ground in saying that the plan of measuring the weather, instead of merely observing it, became general early in the eighteenth century; and that about the middle of the nineteenth century the further improvement was introduced of making meteorological instruments trace their own records, so that the human observer was, to a great extent, dispensed with. Self-registering instruments are now the rule at important meteorological observatories and stations, though they do not, even yet, record all the elements of weather, and at a host of minor stations none of them have yet replaced the eye of the observer.
Now let us see what things go to make up the weather, and how these things are observed by the modern meteorologist.
The pressure of the atmosphere, if not exactly a part of the weather, is so intimately associated with it that we cannot exclude it from our list of weather phenomena. Atmospheric pressure is measured with the barometer, and the importance of this instrument as a key to weather changes is fully recognized—and indeed overrated—by the layman, who sometimes calls it the “weather glass.”