On the Motion of a Bigid System about a Fixed Point, 427 



230. The long iron wire (220.) behaved as before. 



231. Lastly, 1 examined under the same point of view some 

 bodies having an atomic rotatory power on the polarized waves 

 of light and heat. I applied to them the principle of deri- 

 vation mentioned (214.), employing Gourjon's rheometer, and 

 a voltaic intensity proportioned to their conducting power. 



232. Some sugar syrup in a glass tube was placed between 

 the poles of the electro-magnet. The current often Daniell's 

 pairs was made to pass through it a length of some milli- 

 metres. The multiplier was not affected by the magnetiza- 

 tion, whatever was its direction. 



233. A concentrated solution of sulphate of quinine in di- 

 stilled water, traversed by a current of five pairs, gave the 

 same result. 



234. Concentrated tartaric acid, submitted to the current 

 of a single Daniell's pair a length of three centimetres, was 

 not modified by the magnetic induction. 



235. It follows from these researches that magnetization 

 does not alter the molecular condition developed by the pas- 

 sage of an electric current so as to affect its conductibility*. 

 The inverse proposition would also be verified in all proba- 

 bility. If, then, electricity results, as some physicists suppose, 

 in setherial movements depending on the surrounding matter, 

 these movements preserve their intensity when this matter is 

 acted upon by the forces which emanate from the poles of an 

 energetic magnet. This circumstance must be taken into 

 account by the theories which pretend to explain the phae- 

 nomena of electricity and magnetism. 



December 24, 1849. 



LV. On the Geometrical Laws of the Motion of a Rigid 

 System about a Fixed Point. By W. F. Donkin, M.A., 

 F.R.S., F.R.A.S., Savilian Professor of Astronomy in the 

 TJnixjersity of Oxford f. 



THERE is a very simple theorem which seems to be 

 capable of useful applications in the theory of the motion 

 of a rigid system. I do not remember ever to have seen it 

 explicitly stated, though Mr. Boole appears to refer to it in a 

 paper published some time ago in this Journal, which will be 

 mentioned below. I propose here to give a geometrical de- 



* After digesting these notes, I have found in the Traite de Thysique of 

 M. Peclet an isolated observation which agrees with the facts examined 

 above, although the author has not drawn from them any conclusion rela- 

 tive to the nullity of the influence of the magnetism upon the conductibi- 

 lity. (See vol. ii. p. 265, No. 1142; 4th edition, 1847.) 



f Communicated by the Author. 



2 F2 



