STORM TRACK: January 31, 1982 (Volume 5 Issue 2)

The age of weather lore and climatology did not come to a sudden, resounding halt with the invention of the first weather instrument. Indeed, local climatology continues to play a major role in modern forecasting. When all the maps are analyzed, all the data are synthesized, and all the numerical products studied, the successful local forecaster inputs what is known about the local climatology. But as most of us are aware, climatology is not nearly enough to supply the specific and detailed forecast required by today's complex society. The maps, analyses and computer products form the mainstay of the forecast, and basic to all of these is measurement.

The ability to record the four basic parameters of synoptic meteorology (pressure, temperature, humidity and winds) have only been with us a few hundred years. This is not to say that measurements weren't made before then. Wind 'measurements' were made from antiquity in terms of compass points and subjective statements of strength. Many early proverbs in weather lore referred to wind direction. Rainfall measurements were taken in many countries even before the time of Christ. However, the development of instruments capable of moving meteorology into the scientific era awaited the general advances which came with the Renaissance.

The first parameter to be studied was humidity. It seems strange to this author (as it has to many meteorological historians) that this should be the case. Aristotle, by establishing air as a singular element, had successfully 'misled' science over the centuries. His teaching went so far as to assume that evaporating water somehow turned into 'air,' then back to water, during the hydrological cycle. This idea was generally accepted until the 'atomic' theory of matter suggested by Rene Descartes) made its appearance in the early 1600's. It was then that water vapor began to be treated as a separate entity. Yet, the instrument to measure humidity was invented almost two hundred years earlier. In fact, two men working independently appear to have discovered the hygroscopic principle at very nearly the same time. In a book published in 1450 AD, the German mathematician Cardinal Nicolas de Cusa described how he had found that the weight of a ball of wool increased with increasing dampness in the air. A book published two years later by philosopher, writer, architect and scientist Leone Alberti, noted the fact that a dry sponge increases in weight on moist days. He suggested that a sponge on a scale balance could be used to keep track of humidity changes. Some fifty years later, Leonardo da Vinci made two very detailed drawings of hygrometers based on Albertis concept and (somehow), until very recently, ended up with credit for the invention in most texts.

In passing, it should be noted that other means of measuring humidity were devised at later dates. In 1655, Ferdinand II, Grand Duke of Tuscany, while experimenting with condensed moisture on the outside of a drinking glass, discovered the principle later used for the condensation hygrometer. In 1681, Francesco Eschinardi noted the fact that a wetted thermometer cools. This principle led eventually to the psychrometer, or 'wet-bulb' thermometer. Space limitations prevent a detailed discussion of these instruments, and their complex development. The interested reader is urged to consult any good encyclopedia for the particulars.

As with most basic inventions, history has clouded the events leading to the invention of the thermometer. As best this author can reconstruct these events, they are as follows. In 1575 AD, a book was translated concerning the experience of Philo of Byzantium (roughly 300 BC) and Hero of Alexandria. One of Philo's experiments discussed the fact that water can be forced from a nearly closed vessel by applying heat. In the 1590's, Galileo Galilei became interested in this principle. He contained a fluid in a slander glass tube which stood in a goblet of the same fluid. He found that heat would cause the liquid to rise in the tube in proportion to the amount of heat added. His device was actually a 'thermoscope,' and not a thermometer in the strictest sense, since it had no scale (Santorio Santorre, a physician, is credited with first, scaling the thermometer in 1612). Furthermore, although his general hypothesis was correct, the actual device failed to be precise, since it was exposed to atmospheric pressure variations as well as those due to heat,. Evangelista Torricelli deduced this fact in the late 1640's. Torricelli's sponsor, the Duke of Tuscany, then constructed the first instrument in which the fluid was sealed in a glass tube, and which had a fixed scale (1654). All of these events were important to the development of the thermometer -- the decision as to who 'invented' it is left to the reader.

Mention should also be given the man whose name is most often associated with the thermometer, G. D. Fahrenheit, (1686-1736). His contribution involved the calibration of the thermometer to the freezing/boiling points of water. Furthermore, he came up with the idea of using liquid mercury as his fluid, which gave the thermometer a range encompassing the full scale of atmospheric temperatures.

The development of the barometer was triggered in a most peculiar fashion. In 1630, an Italian miner (Giovanni Baliani) wrote a letter to Galileo to inquire why a 21 meter tall siphon wouldn't work. Galileo answered the man by stating that the effect was likely due to the extreme weight of the water breaking away from what was probably a vacuum in the top part of the siphon. This led Galileo to the idea that vacuums might be studied using siphons, and this he suggested to a group of scientists working in Rome -- many of which had been his pupils. One of these (Gasparo Berti) performed the following experiment. A long, hollow pipe standing vertical in a bucket of water, had a small metal cask attached to its upper end. Petcocks were installed both at the lower end of the pipe and in the top of the cask. Next, the cask and pipe were filled with water. The top petcock was closed, then the bottom one opened. Much of the water left the cask, but some remained suspended; AND when the valve on the cask was opened, air rushed in with a loud noise. Another member of the group became fascinated with the concept. In the early 1640's, Torrecilli continued the experiments and decided he might be able to use the principle to measure 'the weight of the air overhead.' With a young pupil, Vincenzio Vivianni, Torrecilli went on to study many variations of Berti's work. Though Torrecilli never built a truly successful barometer, and never scaled the barometers he did build, he is given full credit for the invention -since he was the first to visualize using the apparatus to measure the pressure of the atmosphere. He even went so far as to suggest that barometers be used to track and record changes in pressure over long periods of time. The person that finally had need of an accurate and scaled barometer (and built it!) was Blaise Pascal, who -in 1648- su=gested to fellow researcher Florin Perier, that two calibrated instruments might be used to find the variation or atmospheric pressure with height. One was taken to the top of a high mountain (the Puy-de-Dome) while the other remained below as a control. This was the first 'sounding' of the atmosphere.

To end the discussion on barometers, I should add a few words about the aneroid barometer. In 1663, Pascal suggested a sort of sealed, cylindrical accordian-like contraption which could be used as an alternative method for measuring pressure. But he never built it. The most probable reason that neither man actually constructed their instrument was that the design was beyond the ability of the craftsmen of the day. For the next one hundred-fifty years, ideas were suggested and tried, but it remained for Lucien Vidie to construct a working aneroid in 1843. Most probably, this was simply a case of an idea patiently awaiting the technology to carry it out.

As with instrumentation, quantitative wind measuring devices arrived about the time of the Renaissance. The first known suggestion for an instrument to measure the wind was put forth in a little known book on mathematics by Leone Alberti in about 1450. The device employed a windvane for direction and had a small piece of wood that deflected along a scale when the wind blew. As in the case of the hygrometer, Leonardo da Vinci presented a very detailed drawing of the device in the Codex Atlanticus and was subsequently credited with its invention. However, it is likely that da Vinci was not purposely trying to claim historical credit, since in another work he makes reference to Alberti's anemometer. The mistake seems to have been made by historians, fascinated by all the various devices in the Codex, but not generally aware of his other works. As to the actual building of the device, history is again unclear. It would seem that an anemometer must have been built and used during the 1500's, considering the fascination of the time for instrumentation. Nevertheless, the first record of a working anemometer concerns that constructed by Robert Hooke in 1664. His instrument was similar enough in design and operation to Alberti's that, even though Hooke made no mention of the earlier device, it is assumed the idea for his anemometer came from Alberti or da Vinci.

Thus, by the late 1600's, the instruments necessary to define the atmosphere had been assembled. It was now incumbent on the 'weatherman' to put them to use.