GALILEO AND THE NEW PHYSICS 



scale on a mountain - top whose height was known, 

 why was not this a means of measuring the heights 

 of all other elevations? And so the beginning was 

 made which, with certain modifications and correc- 

 tions in details, is now the basis of barometrical 

 measurements of heights. 



In hydraulics, also, Torricelli seems to have taken 

 one of the first steps. He did this by showing that 

 the water which issues from a hole in the side or bot- 

 tom of a vessel does so at the same velocity as that 

 which a body would acqiiire by falling from the level 

 of the surface of the water to that of the orifice. This 

 discovery was of the greatest importance to a correct 

 understanding of the science of the motions of fluids. 

 He also discovered the valuable mechanical principle 

 that if any number of bodies be connected so that by 

 their motion there is neither ascent nor descent of their 

 centre of gravity, these bodies are in equilibrium. 



Besides making these discoveries, he greatly im- 

 proved the microscope and the telescope, and invented 

 a simple microscope made of a globule of glass. In 

 1644 he published a tract on the properties of the 

 cycloid in which he suggested a solution of the prob- 

 lem of its quadrature. As soon as this pamphlet ap- 

 peared its author was accused by Gilles Roberval 

 (1602-1675) f having appropriated a solution already 

 offered by him. This led to a long debate, during 

 which Torricelli was seized with a fever, from the effects 

 of which he died, in Florence, October 25, 1647. There 

 is reason to believe, however, that while Roberval's 

 discovery was made before Torricelli' s, the latter reach- 

 ed his conclusions independently. 



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