Intelligence and Miscellaneous Articles. 405 



we must alter in a certain proportion the quantities of electricity 

 within the dielectric, and conceive an imaginary distribution of elec- 

 tricity over the surface which separates it from the surrounding 

 medium. 



The theory of magnets and of the phsenomena of paramagnetic 

 and diamagnetic bodies is expressed with reference to the " lines of 

 inductive magnetic action ;" and elementary proofs of the tendency 

 of paramagnetic bodies toward places of stronger magnetic action, 

 and of diamagnetic bodies toward places of weaker action, are given. 

 This distinction of paramagnetic and diamagnetic is not here used 

 absolutely, but indicates a greater or less conductivity for the lines 

 of inductive action than that of the surrounding medium. 



The magnetic phsenomena of crystals are then examined, and 

 referred to unequal magnetic conductivity in different directions ; 

 and the case of a crystalline sphere in a uniform field of force is 

 worked out. 



The laws of electric conduction, as laid down by Ohm, are shown 

 to agree with those of the imaginary fluid, and definitions of quan- 

 tity and intensity are given, which will apply to magnetism as well 

 as galvanism. 



The theory of the attractions of closed circuits, as established by 

 Ampere, is shown to lead to the following results : — 



1 . The total intensity of the magnetizing force estimated along 

 any closed curve embracing the circuit is a measure of the quantity 

 of the current. 



2. The quantity of the current, multiplied by the quantity of in- 

 ductive magnetic action, from whatever source, which passes through 

 it, gives what may be called the potential of the circuit. The ten- 

 dency of the resultant forces is to increase this potential. 



The theory of Faraday with respect to the induction of currents in 

 closed circuits takes the following form : — 



When the quantity of inductive magnetic action which passes 

 through a given circuit changes in any way, an electromotive force 

 proportional to the rate of change acts in the circuit, and a current 

 is produced whose quantity is the electromotive force divided by the 

 total resistance of the circuit. 



The mathematical discussion of the electro-magnetic laws is re- 

 Berved for another communication. 



LI. Intelligence and Miscellaneous Articles. 



ON VOLKNERITE OR HYDROTALKITE, AND THE SO-CALLED 

 STEATITE OF SNARUM. BY C. RAMMELSBERG. 



''PHE author finds that the minerals described by Hochstetter as 

 hydrotalkite, and by Hermann as volknerite, are identical, as 

 indeed was supposed by Hermann. The masses examined by the 

 author are in crooked laminae, and divide, when struck, into crooked 

 parallel fibres ; they arc somewhat flexible, but may be powdered 

 Spec grav. =2-091. Their analyses gave,— 



