CHAPTER IV. 



DISCOVERY OF THE MECHANICAL PRINCIPLES OP 

 FLUIDS. 



Sect. 1. Rediscovery of the Laws of Equilibrium 

 of Fluids. 



WE have already said, that the true laws of 

 the equilibrium of fluids were discovered by 

 Archimedes, and rediscovered by Galileo and Ste- 

 vinus ; the intermediate time having been occupied 

 by a vagueness and confusion of thought on physical 

 subjects, which made it impossible for men to 

 retain such clear views as Archimedes had dis- 

 closed. Stevinus must be considered as the earliest 

 of the authors of this rediscovery; for his work 

 (Principles of Statik and Hydrostatik) was pub- 

 lished in Dutch about 1585 ; and in this, his views 

 are perfectly distinct and correct. He restates 

 the doctrines of Archimedes, and shows that, as a 

 consequence of them, it follows that the pressure of 

 a fluid on the bottom of a vessel may be much 

 greater than the weight of the fluid itself: this he 

 proves, by imagining some of the upper portions 

 of the vessel to be filled with fixed solid bodies, 

 which take the place of the fluid, and yet do not 

 alter the pressure on the base. He also shows 



