Dr. Beer on the Motion of Light. ^ « / ' V,.. 297 



f*< Analysis of the Salt. "' "^ ^ 



0*1320 grm. of salt gave 0-0375 grm. of sulphate of lead 

 =0-0272 grm. of oxide of lead =■ 20*606 per cent. 



Centesimally represented. 



Theory. Found. 



1 equiv. Carmufellic acid . 420 78*947 

 1 ... Oxide of lead . . 112 21-053 2Q-606 



1 ... Carmufellate of lead 532 lOO'OOO 

 Formula PbO,C24H2o 032. 



Atomic Weight of the Acid. 



Theory. Found. Mean. 

 Baryta salt . . 420 4071 ..q 

 Lead salt ... 420 432/^^^^ 



Having finished the investigation of the acid, we concluded 

 that it might have been formed from the oxidation of euge- 

 nine by nitric acid ; but this we found not to be the case. We 

 obtained eugenine in transparent pearly laminse from the di- 

 stilled water of cloves, but in very small quantities ; it is only 

 very slightly affected by strong nitric acid. Dumas assigned it 

 the subjoined formula, which we deem the correct one : — « ).«.. 



C20 H12 04. 



The following are the formulae of the substances already de- 

 rived from cloves : — jlot^ a^ti ,/^ 



Caryophylline . . Q^^H^ O Musprfett. a^ 



■ Carmufellic acid . C^* H^o O^^ Muspratt and Danson. ^. 



Eugenine . . . C^OH^^O^ Dumas. 



Eugenic acid . . C^^Hi^O^ Liebig and Ettling. 



We are at present engaged upon eugenic acid and the neutral 

 oil of cloves ; the subject is extremely difficult, but well worthy 

 of research. 



XLV. On the deduction of FresneFs construction from the for- 

 mulcR of Cauchy for the Motion of Light. By Dr. Beer of 

 Bonn^. 



THE method generally pursued in deducing the optical rela- 

 tions of crystalline media from the formulae of Cauchy for 

 the motion of light, leads to the result, that in such a medium 

 plane waves, whose direction of oscillation is perpendicular to 

 a principal axis, proceed with one and the same velocity, however 



* Communicated by the Author. 



