It should be noted in this connection that the two most important instruments, the thermometer and barometer, were in no way inspired by an interest in meteorology. But the observation made early in the history of the barometer that the atmospheric pressure varied in some relationship to visible changes in the weather soon brought that instrument into use as a "weather glass." In particular, winds were attributed to disturbances of barometric equilibrium, and wind-barometric studies were made by Evangelista Torricelli, Edmé Mariotte, and Edmund Halley, the latter publishing the first meteorological chart. In 1678-1679 Gottfried Leibniz endeavored to encourage observations to test the capacity of the barometer for foretelling the weather.[3] Other questions of a quasi-meteorological nature interested the scientists of this period, and brought other instruments into use. Observations of rainfall and evaporation were made in pursuit of the ancient question of the sources of terrestrial water, the maintenance of the levels of seas, etc. Physicians brought instruments to bear on the question of the relationship between weather and the incidence of disease. The interrelationship between these various meteorological enterprises was not long in becoming apparent. Soon after its founding in 1657 the Florentine academy undertook, through the distribution of thermometers, barometers, hygrometers, and rain gauges, the establishment of an international network of meteorological observation stations, a network which did not survive the demise of the Accademia itself ten years later. Not for over a century was the first thoroughgoing attempt made at systematic observation. There was a meteorological section in the Academy of Sciences at Mannheim from 1763, and subsequently a separate society for meteorology. In 1783, the Academy published observations from 39 stations, those from the central station comprising data from the hygrometer, wind vane (but not anemometer), rain gauge, evaporimeter, and apparatus for geomagnetism and atmospheric electricity, as well as data from the thermometer and barometer. The Mannheim system was also short-lived, being terminated by the Napoleonic invasion, but systems of comparable scope were attempted throughout Europe and America during the next generation. In the United States the office of the Surgeon General, U. S. Army, began the first systematic observation in 1819, using only the thermometer and wind vane, to which were added the barometer and hygrometer in 1840-1841 and the wind force anemometer, rain gauge, and wet bulb thermometer in 1843. State weather observation systems meanwhile had been inaugurated in New York (1825), Pennsylvania (1836), and Ohio (1842).[4]