Galileo also inspired the barometer, through his speculations on the vacuum, which, in 1643, led his disciple Torricelli to experiments proving the limitation to nature's horror of a vacuum. Torricelli's apparatus, unlike Galileo's thermoscope, represented the barometer in essentially its classical form. In his earliest experiments, Torricelli observed that the air tended to become "thicker and thinner"; as a consequence, we find the barometer in use (with the thermometer) for meteorological observation as early as 1649.[1] The meetings of the Accademia terminated in 1667, but the 5-year-old Royal Society of London had already become as fruitful a source of new instruments, largely through the abilities of its demonstrator, Robert Hooke, whose task it was to entertain and instruct the members with experiments. In the course of devising these experiments Hooke became perhaps the most prolific instrument inventor of all time. He seems to have invented the first wind pressure gauge, as an aid to seamen, and he improved the bathometer, hygrometer, hydrometer, and barometer, as well as instruments not directly involved in measurement such as the vacuum pump and sea-water sampling devices. As in Florence, these instruments were immediately brought to bear on the observation of nature. It does not appear, however, that we would be justified in concluding that the rise of scientific meteorology was inspired by the invention of instruments, for meteorology had begun to free itself of the traditional weather-lore and demonology early in the 17th century. The Landgraf of Hesse described some simultaneous weather observations, made without instruments, in 1637. Francis Bacon's "Natural History of the Wind," considered the first special work of this kind to attain general circulation, appeared in 1622.[2] It seems likely that the rise of scientific meteorology was an aspect of the general rationalization of nature study which occurred at this time, and that the initial impetus for such progress was gained not from the invention of instruments but from the need of navigators for wind data at a time when long voyages out of sight of land were becoming commonplace. [Illustration: Figure 1.--A set of typical Smithsonian meteorological instruments as recommended in instructions to observers issued by the Institution in the 1850's. _Top_ (from left): maximum-minimum thermometer of Professor Phillips, dry-bulb and wet-bulb thermometers, and mercurial barometer by Green of New York. _Lower left:_ rain gauge. The wet-bulb thermometer, although typical, is actually a later instrument. The rain gauge is a replica. (_Smithsonian photo 46740._)]