1 64 Intelligence and Miscellaneous Articles. 



for a given strength obtain as great a displacement as desirable. In 

 the models constructed by M. J. Carpentier, who has studied all the 

 details with the greatest care, a displacement of about 10 centim. 

 corresponds to a strength of 10 to 25 amperes according to the 

 apparatus, or to a difference of potential of 100 volts. 



The coils of the amperemeters consist of one or two layers of very 

 thick wires ; they need only have a resistance of 0-01 to 0*02 of an 

 ohm, and thus the apparatus may without inconvenience be 

 introduced into ordinary electric circuits. The coil of the volt- 

 meter is of fine wire, and offers a resistance of about 1700 ohms. 



The curves which represent the displacement of the areometer as 

 a function of the intensity or of the electromotive force of the 

 currents show a bend, in the vicinity of which they do not differ 

 much from a straight line ; the variables have been determined in 

 such a manner as to more particularly utilize this portion of the 

 curve*. 



The apparatus is aperiodic ; it is not sensibly influenced by 

 variations of temperature ; its indications are not altered by the 

 vicinity of masses of metal, or of even very powerful magnets ; its 

 sensitiveness is very great. These various advantages will, we are 

 sure, enable it to perform real services. — Comptes Eendus, Oct. 19, 

 1885. 



ON A NEW SECONDARY ELEMENT. BY M. KALISCHEE. 



The element consists of iron and lead in a concentrated solution 

 of lead nitrate. The iron acting as anode becomes passive, and when 

 the currents are not too strong it becomes coated with coherent 

 thick layers of black peroxide of lead, which protect the iron from 

 contact with the liquid and from decomposition. The change 

 is complete when there is a strong disengagement of gas at the 

 anode, and the solution gives only a slight precipitate with 

 sulphuric acid. In order to prevent a growth of the lead from the 

 kathode to the anode, amalgamated lead in contact with mercury 

 is used. In discharging, the peroxide becomes brown, and 

 ultimately changes into monoxide, to become again changed into 

 peroxide of dark black colour. The electromotive force rises to 2 

 or even 2*5 volts, and when the current is open it sinks to 1*8 volt. 

 When the elements have been discharged for some time, in which 

 the electromotive force has sunk to about 1*7 volt, it rises 

 gradually on opening to 1*76 volt, as in the lead accumulators, and 

 the resistance decreases. 



From its solubility in nitric acid the lead kathode must be 

 occasionally replaced. Carbon can be used instead of iron. — 

 Beiblatter der PhysiJc, No. 7, 1885. 



* The apparatus might be modified in several ways according to the object 

 proposed. I may mention especially the arrangement in which the solenoid and 

 the areometer are brought to a constant relative position. This is easily 

 effected by loading the areometer, or by displacing the coil. In this case the 

 law of the action is simpler, and the graduation of the apparatus is reduced to 

 knowing a single coefficient instead of determining a curve. 



