SUMMARY OF HYDRAULICS. 25 



A Summary of the mofi ufeful Parts of Hydraulics, chiefly ex- 

 tracled and abridged from Eytekoeirfs Handbuch der Mechanik 

 und der Hydraulik. Berlin, 1801. By Thomas Young, 

 M. D. F. R. S. * 



A HE theory of hydraulics has never been carried to a very state of hydrau- 



high degree of perfection upon mathematical foundations alone ;j*. ctheo r y ' a " d 



nor has it hitherto, even with the afiiftance of experiment, plying it to prac- 



been rendered of much practical utility. Newton began the tlce * 



inveftigation of the motions of fluids : Daniel Bernoulli added 



to Newton's propositions much valuable matter, both from 



calculation and from experiment; D'Alembert and many later 



authors have exercifed their analytical talents in inquiries of a 



fimilar nature. But another and a more practicable mode of 



attaining hydraulic knowledge has been attempted by a diftinct 



clafs of inveltigators, at the head of whom Hands the Chevalier 



de Buat. Thefe have begun from experiment alone, and have 



laborioufly deduced from very ample obfervations of the actual 



refults of various particular cafes, the general laws by which 



the phenomena appear to be regulated, or at lealt the formulas 



by which the effect of new combinations may be predicted. 



But it muft be confeffed that thefe formulas, however accurate, 



are too intricate to be retained in the memory, or to be very 



eafily applied to calculations from particular data. 



Mr. Eytelwein, a gentleman already known to the public Mr. Eytelwein'j 



by his tranflation of Buat/s work into German, with important valuabIe com - 



- . t . . pendium, 



additions of his own, and honoured with feveral employments 



and titles relative to the public architecture of the Pruflian do- 

 minions, has collected into this compendium of mechanics and 

 hydraulics, the principal facts that have been afcerlained, as 

 well by his own experiments, as by thofe of former authors, 



the accuracy of adjuftment at N, in which the errors areprecifely the 

 fame as in the common barometer. The double barometer affords 

 an inftance of a lighter fluid floating on a larger j but with a fome- 

 what fhorter fcale than that of fig. 2 — N. 



* This excellent memoir is copied from the Journals of the Royal 

 Inftitution. 



efpecially 



