There are many different types of thermometer. The first recorded device was produced by a Venetian Santorio Santorio who died in 1636. However, his work was based on the efforts of many different scientists. A device called a thermoscope which measured differences in temperatures already existed but in around 1612 Santorio added a measurement scale so that actual temperature could be measured. Prior to that it was only possible to prove that temperatures varied. The first sealed in glass thermometer was developed in 1654 by Ferdinand II the Grand Duke of Tuscany. His innovative use of alcohol to expand along the scale is still in place today. Gabriel Farenheit introduced the mercury thermometer, a far more accurate measuring device and one which is still very familiar to us today. He also devised a fixed measuring scale the 'Farenheit' scale.