ox THE HISTORT OF HYDRAULICS A^'D PNEUMATICJ. ~ S57 



and cylinder were invented by Newcomen, and with Beighton's apparatus for 

 turning the cocks by its own motion, the engine remained nearly stationary 

 for many years. 



As early as the year 1667, the pressure of fluids in motion, and the resist- 

 ance opposed by fluids at rest to the motion of solid bodies, were experi- 

 mentally examined by Huygens, and some other members of the Parisian 

 Academy. Pardies, whose works were published in 1673, attempted to 

 determine, although upon some inaccurate suppositions, the effects of the 

 wind on a ship's sails, under different circumstances. His principles were 

 adopted by Renaud, who published a work on the subject in 1689; their im- 

 perfections were, however, soon after pointed out by Huygens, and by 

 James Bernoulli; and in 1714', John Bernoulli published an extensive 

 treatise on the manoeuvres of ships, which at last compelled Renaud to sub- 

 mit to so many united authorities. 



It must be confessed, that the labours of Newton added fewer improve- 

 ments to the doctrines of hydraulics and pneumatics, than to many other 

 departments of science; yet some praise is undeniably due both to his com- 

 putations and to his experiments relating to these subjects. No person 

 before Newton had theoretically investigated the velocity with which fluids 

 are discharged, and although his first attempt was unsuccessful, and the 

 method Avhich he substituted for it in his second edition is by no means free 

 from objections, yet either of the determinations may be considered in some 

 cases as a convenient approximation ; and the observation of the contrac- 

 tion of a stream passing through a simple orifice, which was then ngw, 

 serves to reconcile them in some measure with each other. His modes 

 of considering the resistance of fluids are far from being perfectly just, 

 yet they have led to results which, with proper corrections, ai-e tolerably 

 accurate; and his determination of the oscillations of fluids, in bent tubes, 

 was a good beginning of the investigation of their alternate motions in 

 general. . , 



o 



The accurate experiments of Poleni were published in 1718: he has the 

 merit of having first distinctly observed that the quantity of water, discharg- 

 "ed by a short pipe, is greater tliau by a simple orifice of the same diameter; 



