Intelligence and Miscellaneous Articles. 149 



was strongly diamagnetic. Under the same circumstances, similar 

 globules of pure copper and silverwere repelled by the electro-magnet. 

 Thus potassium and sodium appear to be feebly magnetic. If 

 they were feebly diamagnetic, as Faraday supposes, the relation 

 between the atomic volumes and the specific magnetism would not 

 be confirmed in their case. 



Movement of rotation due to magnetic induction in the metals, — sodium, 

 potassium, copper, silver, gold, <^-c. 



At the moment when magnetization commences or ceases, the 

 action of the electro-magnet upon sodium and potassium causes 

 energetic movements of repulsion and attraction, due to the produc- 

 tion of induced currents in the mass. A more curious phsenomenon, 

 which must also be attributed to magnetic induction, is the rotation 

 which may be given to a mass of these metals by successive interrup- 

 tions of the circuit of the electro-magnet. 



If a globule or cube of sodium, copper, silver, &c. be placed in 

 any part of the magnetic field, except in the vertical plane which 

 divides the polar surfaces into two equal parts, there is always a 

 rotation when the commutator is manoemTed from right to left, and 

 vice versd, so as to close and interrupt the circuit or change its 

 direction. The rotation is not continuous ; it is intermittent like 

 the ruptures which produce it. Its direction is always from left to 

 right when the mass is towards the operator whose right-hand moves 

 the commutator, and from right to left when it is behind the median 

 vertical plane of the magnet. A succession of ruptures and closures 

 of the circuit, without the reversal of the current, also causes rota- 

 tion, but less energetically than when the current is interrupted and 

 reversed at the same time. 



By these successive magnetizations and demagnetizations, the 

 large copper tube of RuhmkorfFs apparatus may be made to turn for 

 several minutes, so as to give the suspending thread so much torsion 

 that when all electrical movement ceases, the mass rotates rapidly 

 in the opposite direction. 



Electric conductibility of sodium and potassium. 

 The author has endeavoured to measure the conductibility of 

 sodium and potassium. These metals were either cast into thin 

 sticks in glass tubes of 1 to 2 millims., or made into wires. The 

 method of observation followed by him was nearly the same as that 

 described by Pouillet and Becquerel in their researches into the 

 electrical conductibility of metals. His apparatus allowed a resist- 

 ance of 1 millim. in a silver wire of 0"237 in diameter to be easily 

 appreciated. From the numbers obtained, sodium would be placed 

 after the best conductors, — silver, copper and gold, and before tin, 

 zinc and iron. Potassium, which is a worse conductor than sodium, 

 still comes before iron. These metals are equally good conductors 

 of heat. — Comptes Rendus, October 6, 1856, p. 693. 



ON THE MOVEMENTS OP THE FLOATING CRYSTALS OF SOME 

 ORGANIC ACIDS. BY A. SCHKFCZIK. 



Crystals of succinic acid and of benzoic acid prepared in the dry 

 way, when thrown upon the surface of clean water, exliibit pe- 



