Torricelli's name is usually associated with the invention of the barometer but, in fact, he designed many other things also.
At Florence in Italy, there is a museum. Among the exhibits is a telescopic lens which, to the casual observer, appears to be a well-developed lens a little over four inches in diameter. Even an optician will be surprised to know of the precision with which it is made. It is accurate to within a ten thousandth of a millimeter; and we will be far more surprised when we learn that it was made in 1646. Its maker was Evangelista Torricelli. It was made at the time when no modern precision instruments were available. From this fact, we can imagine the amazing degree of accuracy which Torricelli possessed.
Most of us know Torricelli as the inventor of barometer, but only few are aware of the interesting story behind the invention.
According to this story, Grand Duke of Tuscany got a well dug in the courtyard level. In order to bring the water up to ground level, a hand-pump was installed with its pipe dipping in the well water. The pump handle was operated repeatedly, but the water did not rise in the pipe more than the height of 33 feet.
Initially it was thought that there was some defect in the pump. But on careful examination the pump was found to be in quite order.
This incident was reported to the duke but he also could not understand why the pump was unable to bring water to the ground level. In these days, Galileo was the Mathematician to the Grand Duke. So, the problem was referred to him. Galileo at that time was old and practically blind, so he asked his disciple Torricelli to look into it.
Torricelli was aware that a heavier liquid cannot be raised to the same height as a lighter liquid. He selected mercury for his experiment which is more than thirteen and half times heavier than water. He calculated that if the measure of 33 feet is divided by 13.5, the equivalent height to which mercury might rise would be about 30 inches. Therefore, the use of mercury, he thought, would reduce the length of the experimental glass tube to only one yard.
To carry out the experiment, Torricelli took a glass tube of about 1 yard length with its one end closed. He filled it with mercury, closed the open end remained dipped in mercury. When he removed his thumb from the open end from below the mercury level, the mercury in the tube came down slightly and stood at a column length of about 30 inches. The Upper part of the tube became empty. This empty column was named as ‘Torricelli’s vacuum.’ This experiment proved that water by hand-pump cannot be lifted to more than the height of 30 inches x 13.5, that is, about 33 feet and the apparatus used in this experiment later became the basis of evolving the barometer.
Torricelli’s barometer was taken to the peak of a mountain where the height of the mercury column was found to fall down. This proved that as we go above the surface of the earth, atmospheric pressure decrease. Based on this experiment Pascal proved the statement of Galileo that air has weight. Today the barometer has become an essential instrument for weather men.
This great Italian scientist designed serval types of telescopes microscopes and made optical instruments with an almost incredible degree of precision. He was not only an experimental formula for a good mathematician. He discovered the fundamental formula for integral calculus. At the age of 19, Torricelli entered the University of Rome where in later years, he became a professor. His first treatise, A Commentary on the work of Galileo, was published in 1641. He Lived during the period of famous physician Harvey and philosopher and mathematicians like Bacon, Pascal and Galileo.
It was most unfortunate that this great scientist died on 25th October 1647 at the early age of 39. Had he lived for some more years, he would definitely contribute a lot to the advancement of science and technology.