HYDROSTATICS. 349 



the ancients : their whole science consisted in the operations of secret 

 and occult powers ; they transferred from the moral to the physical 

 world, the ideas of affection and hatred ; both celestial and terrestrial 

 bodies had their sympathies and antipathies ; and philosophers con- 

 sidered that they had explained a phenomenon, when they had, after 

 one manner or another, brought it under the influence of these chi- 

 merical agents. 



The Clepsydra, or water-clock, may be considered as an hydraulic Clepsydra, 

 machine, of which the invention is attributable to the Egyptians. This 

 instrument indicated the hours by the successive elevations of the water 

 which entered into a vessel, in quantities, regulated according to the 

 proposed divisions of time, or by means of a hand, which the falling 

 water caused to revolve on a graduated face or dial-plate. Ctesibius, 

 and even some moderns, as Tycho Brahe, Dudley, and others, have 

 not disdained to turn their attention to the improvement of this 

 machine ; the great perfection, however, that has been attained in the 

 construction of clocks and w r atches, renders the clepsydra, in the 

 present day, a mere matter of curiosity. 



Water-mills, which must be classed amongst the most valuable Water-mills, 

 hydraulic engines, were also an ancient invention, of the date of which 

 we are ignorant. An epigram of the Greek Anthology seems to indi- 

 cate that water-mills were first invented in the time of Augustus ; but 

 Vitruvius, who flourished under this prince, in his descriptions, does 

 not speak of them as a recent invention; it is, therefore, highly pro- 

 bable that they were known long before that period. As to wind-mills, Wind-mills, 

 they were not employed in Europe till long after water-mills : some 

 authors pretend, that the former were first invented by the French in 

 the sixth century of the Christian era ; while others assert that we 

 owe them to the Crusaders, who brought them from the East, where 

 they were even then very ancient ; and generally preferred to water- 

 mills, in consequence of the sources of the rivers being much more 

 rare and uncertain in those countries than in Europe. But whether 

 they are the invention, or merely the adoption of Europeans, this is 

 certain that the progress of their improvement was very slow, and 

 that we generally prefer the use of water-mills as more commodious 

 and regular in their operation. 



Bossut, when speaking of these ancient and important constructions, 

 observes, "In viewing so many labours, so many monuments of 

 human genius, the man, alive to gratitude, asks, to whom do we owe 

 all these useful and sublime discoveries ? What honours, what recom- 

 penses, have these benefactors of man received of their country, or of 

 the world at large ? history commonly answers nothing to these in- 

 quiries : while great pains are taken to transmit the names and the 

 exploits of conquerors, who have ravaged the earth, and left traces of 

 misery and destruction in all their steps." 



It is, however, only the construction of certain hydraulic engines 

 that we owe to the ancients ; for they were wholly ignorant of any 



