Intelligence and Miscellaneous Articles. 159 



included a battery of. thirty- six sulphate-of-copper elements, the work 

 of which could either be added to or subtracted from that of the in- 

 duction-machine. 



If F be the electromotive force of Nollet's apparatus, and/ that of 

 the battery, by means of a sine-compass, measuring the intensity of 

 the current in the two cases, we get an approximate value forjf. We 

 have found thus F=4/; that is, that the induction-machine, working 

 with its currents all in one direction, has an electromotive force 

 equal to 144 sulphate-of-copper elements. 



When the apparatus works without the commutator, the currents, 

 acting in groups often in opposite directions, cannot produce a per- 

 manent deflection of the needle unless it be very sensitive. If a vol- 

 tameter be interposed in the circuit, each electrode yields a mixture 

 of hydrogen and oxygen gases. 



In a sulphate-of-copper voltameter electrolysis is also impossible. 

 But it will at once be seen that if by a special arrangement of the 

 voltaic circuit, and without apparently breaking it, one of the series 

 be absorbed, the effects of the other will appear with as much sharp- 

 ness as if the electricity of a battery, or that of an induction- 

 machine with adjusted currents, had been used. 



This remarkable result may be obtained by different means, — 

 among others, if a voltameter with acidulated water be interposed 

 in the circuit, the electrodes of which consist of sufficiently fine pla- 

 tinum. These electrodes are attached to supports, by which they 

 can be more or less immersed in the liquid. One of the wires being 

 immersed in the voltameter, if the other be placed in contact with 

 the surface, its point becomes incandescent. If the electrode be then 

 allowed to sink about 7 or 8 millims. in the acidulated water, it 

 becomes surrounded with a luminous sheath. From this moment 

 we have a current, or rather a series of perfectly polarized currents. 

 The direction of the deflection is such as to show that the electrode 

 with a luminous sheath is positively charged. Interposing in the 

 circuit another voltameter with sulphate of copper, it is seen that 

 the plate which is in metallic contact with the luminous electrode 

 dissolves, while metallic copper is deposited on the other. 



This series of currents, freed from those of the opposite kind, tra- 

 verse as many as thirty-six sulphate-of-copper elements which are 

 arranged in opposition. 



The experiment which has been cited succeeds with either of the 

 electrodes, showing that we can at will modify the effects of each 

 series of currents. 



If the wire be more deeply immersed in the voltameter, the lumi- 

 nous sheath disappears, and the series of currents which was ab- 

 sorbed ceases to be so. — Comptes Rendus, November 4, 1867. 



METHOD OF GALVANICALLY PRODUCING HOLLOWS AND RELIEF 

 WITHOUT THE AID OF VARNISH. BY M. BALSAMO. 



It is generally known that, in vibrating plates, points can be pro- 

 duced where the disturbance is almost null, and others where it is very 

 great, — that is to say, nodal lines and segments. This is effected by 



