Thermoscope

Devices employing both heat and pressure were common during Galileo's time, used for fountains, nursing, or bleeding in medicine. The device was built from a small vase filled with water, attached to a thin vertically rising pipe, with a large empty glass ball at the top. Changes in temperature of the upper ball would exert positive or negative pressure on the water below, causing it to rise or lower in the thin column. Essentially, thermoscopes served as a justification of sorts regarding what is observed or experienced by the senses – that the device's basic agreement with the indications of the senses generates initial confidence in its reliability. Large thermoscopes placed outdoors appeared to cause perpetual motion of contained water, and these were therefore sometimes called perpetuum mobile. Galileo's own work with the thermoscope led him to develop an essentially atomistic conception of heat, published in his book Il Saggiatore in 1623. ==History==

Philo of Byzantium is credited with the construction of the first thermoscope (or Philo thermometer), an early version of the thermometer. It is also thought, but not certain, that Galileo Galilei discovered the specific principle on which the device is based and built the first thermoscope in 1593. In the 17th century Galileo mentioned to his friend Cesare Marsili that he invented a thermoscope as far back as 1606. The inventor could be his physician friend Santorio Santorio or another person of the learned circle in Venice of which they were members. What is certain is that the thermoscope had started circulating in market squares during Galileo's time. Shortly afterward, in 1617 Giuseppe Biancani published the first clear diagram. The device at this time could not be used for quantitative or standardized measurement and used the temperature of air to expand or contract gas, thereby moving a column of water. The device was improved by early German scientist Otto von Guericke in the 17th century. In 1701 Ole Christensen Rømer effectively invented the thermometer by adding a temperature scale (see Rømer scale) to the thermoscope. ==See also==