With the great revival of learning which took place in Southern Europe in the latter part of the fifteenth century new light came to be thrown on the classical philosophies which still ruled men’s minds, and modern science was born. New views on natural phenomena began to irradiate, and, sweeping aside the myths and traditions which surrounded and stifled them, the votaries of the “new science” began to formulate opinions of the boldest and most unorthodox description.[70] The true laws of the equilibrium of fluids, discovered originally by Archimedes, were rediscovered by Stevinus. By the end of the sixteenth century the nature of the physical universe was become a pursuit of the wisest men. To Galileo himself was due, perhaps, the first distinct conception of the power of steam or any other gas to do mechanical work; for “he, the Archimedes of his age, first clearly grasped the idea of force as a mechanical agent, and extended to the external world the conception of the invariability of the relation between cause and effect.”[71] To his brilliant pupil Torricelli the questioning world was indebted for the experiments which showed the true nature of the atmosphere, and for the theory he proclaimed that the atmosphere by its own weight exerted its fluid pressure--a theory which Pascal soon confirmed by the famous ascent of his barometer up the Puy-de-Dôme, which demonstrated that the pressure supporting his column of mercury grew less as the ascent proceeded. Giovanni della Porta, in a treatise on pneumatics published in the year 1601, had already made two suggestions of the first importance. Discussing Hero’s door-opening apparatus, della Porta showed that steam might be substituted for air as the expanding medium, and that, by condensing steam in a closed vessel, water might be sucked up from a lower level by virtue of the vacuum so formed. And a few years later, in 1615, Solomon de Caus, a French engineer, had come to England with a scheme almost identical with della Porta’s, and actually constructed a plant which forced up water to a height by means of steam. Shortly afterwards the “new science” received an accession of interest from the invention, by Otto von Guericke of Magdeburg, of a suction pump by which the atmospheric air could be abstracted from a closed vessel.