Meteorology known as the first "anemometer". In 1607, Galileo Galilei constructed a thermoscope. In 1611, Johannes Kepler wrote the first scientific treatise on snow crystals: "Strena Seu de Nive Sexangula (A New Year's Gift of Hexagonal Snow)". In 1643, Evangelista Torricelli invented the mercury barometer. In 1662, Sir Christopher Wren invented the mechanical, self-emptying, tipping bucket rain gauge. In 1714, Gabriel Fahrenheit created a reliable scale for measuring temperature with a mercury-type thermometer. In 1742, Anders Celsius, a Swedish astronomer, proposed the "centigrade" temperature scale, the predecessor of the current Celsius scale. In 1783, the first hair hygrometer was demonstrated by
Christian Mayer (astronomer) of mathematics and physics at Heidelberg. By this age, however, he had developed a strong interest in astronomy. He was appointed Court Astronomer at Mannheim, and was tasked with selecting the instruments for the new observatories at Schwetzingen and Mannheim. With these completed, he was able to pursue his astronomical studies, and published numerous works. In 1769 he was invited to St. Petersburg to observe the transit of Venus, which he did together with Anders Johan Lexell. In 1773, the Jesuit order was dissolved by Pope Clement XIV, and consequently he was removed as Court Astronomer. However he was still