French National Inftitute* 4CI 



nti a flexible wire or fluid. He determines, in a fpecial 

 manner, the conditions of this equilibrium from this princi- 

 ple, that the centre of gravity of the fyfiem mutt defcend 

 as low as poffible ; and details various fituations of equili- 

 brium, either fixed or tranfitive, which the propofed bodies 

 may affinne. 



experimental ph,ilosophy. — Determination oftbeLi- 

 it ujily of the Action lukicb Magnetic Bars exercife on dif- 

 J'crent Metals purified by the ordinary PrvccJJ'es. 



\n purfuing his rcfearches on the a&ion which magnetic 

 bars exerqife on all bodies, C. Coulomb has been able to 

 mcrtfure the ' intenfity of this action for the different metals 

 brought to that ftate of purity which remits from the com- 

 nioiroperations of refining. 



He formed .fmall cylinders of wax, into which he intro- 

 duced different quantities of iron-filings uniformly difperfed 

 over the whole mafs, and, by meafuring the action which 

 they experienced from magnetic, bars, has deduced the law 

 according to which the magnetic force decreafes in propor- 

 tion as the quantitity of the iron mixed is leflened. With 

 thefe two data he determined the very fmall quantity of iron 

 that remained in art 'ingot of filver fufed with an equal por- 

 tion of iron by C. Guv ton, and which in the operation had 

 appeared to feparate itfelf very exactly from the fecond metal. 



This (ilver, diffolved in nitric acid and precipitated by 

 prufliate of foda, gave no indication of the prefence of iron ; 

 it however experienced, in a fenfible manner, the influence 

 of the magnetic bar, and in fuch a manner as to fhow that 

 it dill contained iron. By comparing this action with that 

 of the fame bar on the cylinders above mentioned^ C. Cou- 

 lomb has found that there remained in the piece of filver ^. 

 of iron. He found by the fame method, that if the action of 

 the magnetic bar on a plate of filver purified by cupellation, 

 or extracted from the muriate, ought to be afcribed to the 

 prefence of iron, the quantity cf the latter metal prefent will 

 amount only to tt*W? P art « This quantity, which may be 

 confidered as infinitely fmall, would, however, be in fuch a 

 ftate of divifion that there would be no molecule of filver 

 which did not contain a portion of iron. ^ 



On the nth of Pluviofe C. Guay Luffac prefented to the 

 Infiitute a memoir on the dilatation of various elallic fluids 

 by the agency of heat. In examining the experiments of 

 different philosophers on this fubject, he ftates that the great 

 difcordancy in their refults is chieflv owing to the prefence of 

 water in the apparatus employed, which being diffolved by 



Vol, XIII. No. 52. Cc the 



