Subjedls of ex- 

 periment. 



Extreme deli- 

 cacy of the fuf- 

 frenfion. 



14-J SCIENTIFIC NEWS< 



itfelf according to the direction of the two bars; and that U 

 they were turned from this direction, they always recovered it, 

 after ofci Nations of which the number was often more than thirty 

 per minute. It was therefore eafy in every cafe to determine, 

 from the weight and figure of the needle, the force which had 

 produced the ofcillation. 



Thefe experiments were fuccefTively made with fmall needled 

 of gold, filver, copper, lead tin, fmall cylinders of glafs, a piece 

 of chalk, a fragment of bone, and different kinds of wood. 



Citizen Coulomb has proved, in a former memoir; that the 

 force of torfion of the filk thread is fo flight, that in order to 

 draw it round through the entire circle, it would require a force 

 fcarcely equal to the one hundred thousandth part of a grarrf 

 (or about one feven hundredth of a grain). A quantity fo mi- 

 nute cannot therefore fenfibly derange, the meafure of magnetic 

 force in the different bodies, and its effe6t even, if it were ad- 

 mitted to be of perceptible magnitude, may alfo be urged in 

 proof of the general conclufi on of Citizen Coulomb, becaufe 

 the magnetic power muft overcome this refiftance of the thread 

 in order to manifeft itfelf. Our author gives, in the third vol. 

 of the Memoirs of Natural Philosophy and Mathematics of the 

 National Inftitute, a very fimple formula to determine the! 

 magnetic force Of a body from the time of its ofcilations, and 

 he means to fhew in another memoir, the method of determine 

 ing this refult in different bodies of the fame figure placed be- 

 tween the poles of two bars. He thinks it now proved, that: 

 all the elements which enter into the compofition of our globe, 

 are fubje&ed to the magnetic power, and that the whole mafs 

 collectively forms one tingle magnet, 

 ©bfervations. In favour of thofe who might be defirous of repeating his 



experiments, and rendering them very fenfible, the author re~ 

 marks, that the method of fucceeding confifts in diminifhing 

 the fize of the ofcilating bodies. From fome effays, of which 

 the refults terminate this memoir, it feems to follow, that tne 

 accelerating forces are inverfely as the maffes are very nearly 

 in the direel proportion of the furfaces ; but Citizen Coulomb 

 gives this rule only as a firfl deduction, which requires to btf 

 confirmed. 



ERRATA. 

 In Mr. Cruickfhank's paper, p. 43, end of the firft paragraph, for faults 

 xtidfaSii j and p. 46, 1. 26, fcr computed read compiled. 



