1832.] Miscellaneous Intelligence. 477 



4. Rain at Chira Punji, 



from 1st Septi 



>mber to 



9th October, 1832, registered by 







W. Cracroft, Esq, 









inches. 





inches. 





1 0.000 



1 



1.195 



16 



0.305 





2 0.000 



2 



1.117 



17 



1.050 





3 000 



3 



1.575 



18 



6.375 





4 0.000 



4 



2.510 



19 



1.850 





5 0.125 



5 



4.680 



20 



0.130 





6 0.000 



6 



1.689 



21 



0.760 





7 3.015 



7 



0.000 



22 



0.985 





8 12.650 



8 



not meas. 



23 



4.600 



Rain in Sept. 55.309 



9 



4.232 



24 



5.010 



In 



2 days of Oct. 15.790 



10 



9.494 

 6.332 



25 



26 



0.000 

 0.000 



Al 



ready regt. 154.690 



11 







12 



0.000 



27 



0.000 



in 



four months, 225.789 in. 



13 



0.085 



28 



1.235 



M, 



aximura temperature, 



14 



0.000 



29 



0.000 





16th 81o 5' 



15 



0.000 



30 



0.000 



M 



inimum, 29th.. . . 60 



5. Electric Spark from the Magnet. 

 The modes in which Sig. Nobili, in Italy, Mr. Faraday, and Mr. Ritchie, in Lon- 

 don, and Mr. Forbes in Edinburgh, have successively arrived at this satisfactory 

 result of their researches, are now given to the world. 



Signor Nobili was the earliest in point of date, but he was led to the discovery 

 of the spark entirely by the theoretical views and previous experiments of Mr. 

 Faraday, who also arrived at the same conclusion immediately after, and with- 

 out a knowledge of his rival's labours. The apparatus necessary to display the 

 phenomenon is exceedingly simple. The following are the views upon which it is 

 framed. 



" The voltaic pile gives a spark only when composed of a certain number of 

 pairs of plates. A single Wollaston's voltaic element yields it ; and when of a 

 certain activity, produces it constantly at the surface of the mercury, to which the 

 conjoining wires destined to close the circuit are conducted. In the voltaic pile, 

 having a certain degree of electric tension, the sparks pass between the zinc and 

 copper poles, either in the case of opening or of closing the circuit. In a single 

 Wollaston's element, the tension is feeble and the spark occurs only when the cir- 

 cuit is interrupted. At that moment, the current, which was before moving, accu- 

 mulates as it were at the place of interruption, and acquires the intensity necessary 

 to cause the spark. Such tension is wanting in the other case of closing the cir- 

 cuit, and the spark also is absent. 



"The currents developed in the electro-dynamic spirals by virtue of magnetism 

 are also in motion, but circulate only for the moment during which they are ap- 

 proaching to or receding from the magnet. 



*' It was, therefore, Sig. Nobili and Antiniori concluded, in one of those two mo- 

 ments that the circuit ought to be opened in making the experiment for the spark." 

 Experiment. A coil of wire is wound round the cross-bar or armour of a horse- 

 shoe magnet ; the ends of the wire are brought away to a short distance from the 

 bar, and bent so as to meet ; and, to ensure their contact, a disc is attached to the 

 extremity of one wire, upon which the point of the other impinges at right angles : 

 the contact is then made perfect by amalgamation witb mercury. When the bar 

 is separated from the magnet or brought to it, the jerk at contact separates the 

 points of the wire for an instant, and a spark is seen to pass from one to the other, 

 and when the armour is suddenly removed it is again visible : the experiment may 

 be repeated at pleasure. — Phil. Mag. Ixvi. 406* 



