( 608 



99,91 99,93 99,96 ') 

 Reckoned for : 



Hematite Magnetite 

 Fe 70 72,41 



30 27,59. 



So that my conclusion is that wc have not to do witii Magnetite but 

 Avith Hematite. 



The results of mv i-esearciies are in conscciuence the foilowins; : 

 I'*'. That 1 have had to do Avith Henialile AA'ith very obvious 

 magnetism and a black streak, a\ hich in i-iibbing along the outlines 

 shoAvs a brown tint (Avhicii generally eveiy black streak does) and 

 not Aviih a })seudoniorphosis from ^lagnetite to Hematite. 



2""'- That Avhere in literatui-c of this occurrence of Hematite has 

 been spoken, no analysis has boon added, though the magnetism and 

 the black streak have been obser\od moi-o than once. 



3^'*^. That it is desirable to convince oneself of the chemical com- 

 position Avith every "Eisenrose", Avliich shoAvs diese characteristics. 



Physics. — '' Contiihutions to the theory of electron.^." I. By Prof. 



H. A. LORENTZ. 



SbnpUjicatkm of the fu neb i mental equation.^ hi/ the introduction 



of new units. 



§ 1. \i' all ([uantilios are expressed in electromagnetic units, as I 

 haA'e done in former papers, the relations between the Aolume-densit}' 

 Q of the charge of an electron, the velocity o of its points, the 



1) 1 here by have to mention that fust the figure for the oxygen was determined 

 by reduction in a hydrogen-current und weighing of the water absorbed by CaCb; 

 that after that the figure for the iron was determined by dissolving the reduced 

 mineral in dilute HoSO^ and making a tilra'ion ot this solution (after reduction 

 in a HjS-current and after removing the HoS by boiling in a C0;> atmosphere) 

 with a KMnO^-solution, of which 1 cM"' corresponded with 8,9 m.G. Fe. 



The presence of Ti was shown as follows : the mineral was melted together 

 with KHSO^, the fused mass dissolved in cold water. This solution together with 

 HoO^ gave tlie well-known orange colour of TiOs. Moreover after adding a 

 little HXO;;, tlie Ti after having been boiled precipitated as white TO^. The 

 accompanying mineral, whicli in microscopic examination proved to be adularia, 

 was lemoved as mucli as possible. 



