French National Injlitiile. 183 



About the year J 756 Maver had remarked ibis tint in the 

 nineteenth of /)i/iv.f, wliich he denotes in the regiltcr of his 

 obfervations bv the epithet o^ rubicutuhi, as. we have feen by 

 the copv fenl to us bv M. Liehtenibersf of all the obfervations 

 made bv Maver on the dav on which he obferved the planet 

 of Herfehel. Michell and liailli fuppofe that the colour of 

 the (lars mav depend on the different inteiifity of their fire, 

 or the degree of their inflanmiation ; and that the red colour 

 may indicate a fire decrealing. Under this idea it might be 

 of importance to examine the changes of colour which the 

 Itars experience. However, thefe variations, if they exifi, 

 are doubtlefs excecdin<>;lv flow; for the diflerent fliades at 

 prefent remarked between Autares, Arflurus, Aldebaran^ 

 Syriiis, and the Lyre, cxiftcd in the time of Ptolemy. 



Extrati from </ ^Ictno'ir on the Degree of Mi:gnet'ifm acquired 

 by Bars oj" Steel of' dTjf'ercjit Thicknejs, ml on Jonie Utfults 

 in regard to the Magnetic Needle, hj C. Coulomb. 



Almoft; all the magnetic phsenomena can be fubjefled to 

 calculation if we fuppol'e in Cteel two magnetic fluids, in each 

 of which the molecidte repel each other in the invjrfe ratio 

 of the f(juares of the dill^ances, and attraft in the i'ame ratio 

 the particles of the otlier fluid. This law was proved by 

 Coulomb in the Memoirs of the licademy for 1786, from 

 experiments which appear decifive. 



When fteel is in its natural (tate, and not magnetized, the 

 two fluids are neutralized by each other; that is to fay, they 

 keep each other muluallv in equilibrium, and no longer exer- 

 cifc any action, fince one of the fluids attracts a magnetic 

 molecula with the fame force as the other repels it. 



When the fluids are feparated they tend to unite and to 

 neutralize each other; and they would indeed unite were 

 there not a coercive force which oppofes this union. This 

 force mav be either, th<- adhefion of the molecuhe of the fluid 

 to the (reel, or the friction which they experience in paffing 

 from one pouit to another. „ 



The author has proved [l\Thno'ires dc I'Academie 1787, 

 p. 491) that whether the two fluids were feparated and car- 

 ried each to an extremity of the bar, or wliether they were 

 orilv dilplaced in eaclnnoleculaof the flcel without the power 

 of palfiii<i from one molemla to another, calculation gave the 

 fime relidt. He has proud at the fame time that the latter 

 fuppofition is the only one which can agree with experience. 



According to thefe fuppofitions, a bar (»f flcel may accjuire 

 cvt-rv degree of niaiineiifui, provided that there is no point in 

 it wiierc the rclult of the aWion of all the moleculsc of the 



M 4 fiuiU 



