Refracting telescope
Refractors were the earliest type of optical telescope. The first practical refracting telescopes appeared in the Netherlands about 1608, and were credited to three individuals, Hans Lippershey and Zacharias Janssen, spectacle-makers in Middelburg, and Jacob Metius of Alkmaar. Galileo Galilei, happening to be in Venice in about the month of May 1609, heard of the invention and constructed a version of his own. Galileo then communicated the details of his invention to the public, and presented the instrument itself to the Doge Leonardo Donato, sitting in full council.
Thermoscope
It is thought, but not certain that Galileo Galilei discovered the specific principle on which the device is based and built the first thermoscope in 1593. 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 has started circulating in market squares during Galileo's time. The development of the actual device is attributed to four inventors namely, Galileo, Santorio Santorio, Robert Fludd, and Cornelius Drebbel. However, the general pneumatic principle of the thermoscope was used in the Hellenic period, and it was written about even earlier, by Empedocles of Agrigentum in his 460 B.C. book "On Nature".