184 Frertcb National Injlitute. 



be very little. It becomes' very difficult to eftimate it by th« 

 ufual means, and ftill more difficult to difcover what belongs 

 to the different terms of the formula. To accomplifh thefe 

 points it would be neceflary to have a kind of meafure which 

 might determine, with fufficient accuracy, the fmallefl forces, 

 and afford the means of varying the velocity at pleafure, in 

 order to render the different terms of the formula prevalent 

 in turns. 



All thefe advantages C, Coulomb has found united in the 

 machine with which he meafures the torfion of a wire fuf- 

 pended in a vertical pofition. He has already derived great 

 advantages from this indrument in other branches of phy- 

 fics, and he has given in former memoirs theorems refpdft- 

 ing the force of torfion, or the means of eflimating it in 

 weicht. With this aid he has demonftrated the real law of 

 refiftance where the motion is flow ; a law which had efcaped 

 Newton, Bernoulli, and Gravefend. It refults from his ex- 

 periments : 



ifl:. That where the motion is very flow, the refiftance is 

 proportional merely to the velocity, and the term depending 

 on the fquare becomes infenfible. 



ad, That the height of the fluid above the body immerfed 

 in it, does not fcnfibly increafe the refifl:ance. 



3d, That the refiftance arifes only from the coherence of 

 the parts of the fluid with each other, and not from their 

 adhefion to the body immerfed in them. 



4th, That the refiftance in limpid oil is feventeen times 

 and a half greater than in water. 



We fliall omit feveral other refults which will be read 

 with, pleafure in the memoir itfelf, and only add, that the 

 acrcenipnt between the different trials is fo great as muft 

 aftonilh thofe not acquainted with the accuracy and precifion 

 of the inftrumcnt with which C. Coulomb has enriched 

 natural philofophy. 



C. Prony prcfented to the Clafs the three firft parts of a 

 work entitled Mechanical Philofophy, or. An Analyfis of the 

 different Parts of Equilibrium and Motion. 



Since the invention of the new calculus, the province of 

 xneghanics has been confiderablv enlarged. A great number 



of 



