French National Injtitute, 279 



•fluenre of the arrinciai macrntl; But this atftion, though 

 real, has not tlie fiitie force in all bbdits; and in the greater 

 part u is neceflarilv v'erv ('.i.all, fince it has hitheiio eluded 

 the nonce of jihiioftiiiliers. 



C. Coulo lih gave to each of the bodies which he tried the 

 form of a cylindt-ror fmatl bar: in this ftate he fufpended 

 them hy a : bread of liik, fnch as it i-> when taken from 

 the cod, and placed hem between the oppofite poles of two 

 bars of Ittel. The fiik thrLad can fufta'm no greater weight 

 thati eight or icn grammx^« without breaking; it was there- 

 fore necelHirv to reduce to verv ftnail liimenlions the needles 

 formed of the diiferent bodies bibjefted to experiment. 

 C. Conlomb ma.le them of fronn fcveu l.» eight millimetres 

 in thicknefs: thofe of metal he made only one-third of that 

 fize. 



For thefe experiments he placed the bars of fteel in the 

 fame Itraight line, their oppofite poles being diftant froin 

 each other five or fix niillimcires more than the length of the 

 needle which was to ofcillate between them. The refult of 

 thefe experiments has fliown, that of whatever matter the 

 needles cnnlitied, they always arianoed tbeniiebe'' exaol;lv in 

 the direction of the two bars; mid that, if removed from this 

 direftion, thev alwavs returned to it by ofciil itions, the 

 numi-.cr of whi^-h was often thirty in a minute. The weight 

 and figure of tfie needles being given, it was therefore eafy 

 to deter nine the force which produced thefe ofcillations. 



Thefe experimenis were made in fucceflion with fmall 

 plates of gold, filver, copper, lead, and tin; fniall cylinders 

 of glafs, a bit of chalk, a fragment of bone, and dilVercnt 

 kinds of wood. ~ 



Phyjical Part, rend by Lacepede, fecretary. 



ChemiJIry and Mi crology. — C Mongc lias given an ac- 

 count of feveral important oblervationsin regard to the theory 

 of the earth, and which he made duraig bib travels in Italy 

 and Kgvpt. 



C. Ramon has given obfervations on the ftrufture of the 

 mean and inferior mountains of the valley ot Adour, one of 

 the moll intereliing in the I'yreuees. 



C. Lamarck has publifhed an intcreiling work entitled 

 Hydrogeotogy, or Rf/'ciircl\'i on the hijlueii, ■ which the Wa- 

 ters have on the Surface of the iiarth, on the Cavfes of the 

 Exijience of the Ba/'on of the Seas,' its Difyi cement, &€. 



C. .Setruin, aflbciat", read two menioi'- refpcd-ling cinna- 

 bar; in which he eiulcivoiirs to prove ih.it cthiops and cin- 

 nabar are only compounds of fulpiuir and mercury, without 

 oxygea and hydrogen : itiat ihelc two lubltances tliffcr.frcm 

 JS 4 each 



