(1566 – 1624); the first showing a scale and thus constituting a thermometer was by Santorio Santorio in 1625. This was a vertical tube, closed by a bulb of air at the top, with the lower end opening into a vessel of water. The water level in the tube is controlled by the expansion and contraction of the air, so it is what we would now call an air thermometer. The word thermometer (in its French form) first appeared in 1624 in La Récréation Mathématique by Jean Leurechon, who describes one with a scale of 8 degrees. The word comes from the Greek words θερμός, thermos, meaning "hot" and μέτρον, metron, meaning "measure". The above instruments suffered from the disadvantage that they were also barometers, i.e. sensitive to air pressure. In 1629, Joseph Solomon Delmedigo, a student of Galileo and Santorio in Padua, published what is apparently the first description and illustration of a sealed liquid-in-glass thermometer. It is described as having a bulb at the bottom of a sealed tube partially filled with brandy. The tube had a numbered scale. Delmedigo did not claim to have invented this instrument. Nor did he name anyone else as its inventor. In about 1654, Ferdinando II de' Medici, Grand Duke of Tuscany (1610–1670) did produce such an instrument, the first modern-style thermometer, dependent on the expansion of a liquid and independent of air pressure. Many other scientists experimented with various liquids and designs of thermometer. However, each inventor and each thermometer was unique — there was no standard scale. Early attempts at standardization added a single reference point such as the freezing point of water. The use of two references for graduating the thermometer is said to have been introduced by Joachim Dalence in 1668 although Christiaan Huygens (1629–1695) in 1665 had already suggested the use of graduations based on the melting and boiling points of water as standards and, in 1694, Carlo Renaldini (1615–1698) proposed using them as fixed points along a universal scale. In 1701, Isaac Newton (1642–1726/27) proposed a scale of 12 degrees between the melting point of ice and body temperature. Era of precision thermometry In 1714, scientist and inventor Daniel Gabriel Fahrenheit invented a reliable thermometer, using mercury instead of alcohol and water mixtures. In 1724, he proposed a temperature scale which now (slightly adjusted) bears his name. In 1742, Anders Celsius (1701–1744) proposed a scale with