30 REPORT — 1842. 



the usual tension upon the coil, and so as to produce contrary magnetism, the 

 needle moved from 27° to 12°. 



Thus the said current acting so as to strengthen the magnetism of an iron which 

 caused the needle to deviate 10°, increased it so much that it deviated 21°. But that 

 magnetism being removed, and the same experiment being then repeated by causing 

 the current to act in an opposite direction, the deviation of 10° west was changed 

 to 3° east. 



A given current, therefore, and the same degree of another magnetizing action 

 has less effect when so directed as to strengthen, than when so as to neutralize the 

 magnetism. 



Which things being established, it becomes easy to explain the variations in the 

 magnetic susceptibility of iron, of which we are here treating. 



Let us suppose an iron magnetized with some force, as, for example, that the 

 needle of the magnetometer may deviate 40°, and weaker currents being afterwards 

 made to circulate round it, let it be reduced to the point of no deviation. This iron 

 will be in such condition, that by a given current which circulates around it, it will be 

 more strongly magnetized, when this serves to make the south pole appear from the 

 same part at which it appeared when it was strongly magnetized, than when the 

 same current is made so to act that it tends to produce the south pole from the 

 part on which the lesser currents, which were made use of to neutralize the first 

 magnetization, tended to produce it. 



In fact, if with these discharges of the Leyden jar I have produced so many magnetic 

 systems, which now exist in the said iron, by causing to circulate around it a given cur- 

 rent, so directed as to tend to magnetize the iron, in the direction in which it had been 

 strongly, it is very true that it will but little strengthen the magnetic system having 

 the south pole towards the west, but it is true also that it will much neutralize the 

 weaker and opposite systems. Hence a polarity ought to be manifested in the said 

 direction, stronger than that which would be obtained with the same current before 

 the iron had been treated in the manner we have mentioned. Since things being 

 placed in the state of the preceding experiment, that is, the magnetism of the iron 

 being neutralized, if an equal transitory electric current is made to act so as to 

 produce in the iron the south pole on the opposite part, the neutralization of the 

 strong magnetic system should be 6mall, and equally small the strengthening in the 

 opposite magnetic systems, and thence the resulting magnetization will appear weak. 

 I conclude this abstract with describing an experiment, in which, with a union 

 of iron wires differently magnetized, the phaenomena are imitated which the facts 

 above stated make us suppose to exist in an iron when its magnetic susceptibility is 

 changed. 



I magnetized a bundle of six iron wires eight centimetres long, and weighing in 

 all thirty-seven decigrammes, deprived of magnetism, and not changed in magnetic 

 susceptibility, so that the needle of the magnetometer was caused to deviate 48° to- 

 wards the west. With five other iron wires, slightly magnetized and in different 

 degrees, united to the above bundle so that the north pole of the latter came in con- 

 tact with the south poles of the former, I made a bundle of eleven wires which did not 

 cause the needle to deviate. Having placed this bundle in the usual coil, and dis- 

 charged upon it the small Leyden jar with the tension of 10°, and so directed as to 

 produce the north pole in the said bundle, on the side where the six wires united to- 

 gether had it, such a magnetization ensued that the needle deviated 49°. And the 

 experiment being repeated from the beginning, and the jar with the same tension of 

 10° being then discharged upon the coil, but directed contrarywise, a magnetization 

 of only 22° ensued. Stefano Mahianini. 



Modena, 01st May, 1842. 



CHEMISTRY. 



On the Electrolysing Power of a simple Voltaic Circle. By Professor 

 Schonbein of Basle. 



The object of the experiments detailed in this paper, is to investigate the conditions 

 under which the electrolysis of water takes place when a feeble electric current is 



