332 SEC. 10. ELECTRICITY. 



The detailed description and theory of Kohlrausch's various apparatus may 

 be found as under : 



Poggendorff's Annalen, Vols. 72 and 7 4 for the torsion-electrometer. 

 Vol. 88 for the sine-electrometer. 



Vols. 75 and 88 for the condenser. 



The apparatus which are exhibited show the forms which Th. Schubart 

 (late of Marburg, and now of Ghent) makes at the present time. A good 

 description of the present forms is given in Wiillner's " Lehrbuch der Experi- 

 mental-Physik," Vol. 4, 3rd edition, p. 159, and p. 299. 



1431. Edelmann's Quadrant-electrometer. 



M. Th. Edelmann, Munich. 



1431a. Electrometer for measuring potentials, and par- 

 ticularly the potential of an accumulator at the moment of the 

 discharge. Prof. Augustus Righi, Bologna. 



143 Ib. Induction Electrometer. 



Prof. Augustus Right, Bologna. 



A caoutchouc tube carrying several copper rings is wrapped round the non- 

 insulated pulleys (2, 4). If the insulated inductor (1) is charged, the rings 

 go from (2) to conductor (3), with charges of contrary sign, and these 

 charges remain in the insulated conductor (3). For, as the rings touch the 

 conductor (3) by means of a little pulley placed in its interior, the charge 

 preserved by any single ring is slight. For a very small charge of the 

 inductor, the conductor (3) acquires a charge great enough to be shown by 

 a gold leaf electroscope. If the inductor is uncharged, and the pulleys and 

 the rings are of the same metal and very clean, the conductor (3) remains 

 uncharged. 



In open places the conductor (3) is charged by the sole influence of atmo- 

 spheric electricity. 



1432. Ronalds' Electrical Apparatus, as employed by 

 him at the Kew Observatory ; consisting of a principal conductor, 

 with its glass support, umbrella, and heating apparatus ; its vol- 

 taic collecting lantern ; Volta's electrometers and sights ; a Henley 

 electrometer; a Grourjon galvanometer; a discharger, or spark 

 measurer ; and a Bennet's gold-leaf electroscope. 



Kew Committee of the Royal Society. 



Apparatus erected in the equatorial room of the Kew Observatory, in 1843, 

 by Mr. Francis Konalds, for the purpose of observing atmospheric electricity, 

 .described in the British Association Keport for 1844. 



It consists of a principal conductor, which is a stout copper tube, passed 

 through a large aperture lined with sealing-wax in the roof of the building 

 in which the instrument was placed, and carrying an inverted copper tray, to 

 exclude rain. 



The tube is supported by a stout glass core, which is kept in a dry state 

 by a copper funnel passing up its interior, kept contantly heated by a small 

 lamp. 



A second lamp is enclosed in a Volta's collecting lantern, fixed to the top 

 *of the collecting tube. 



To the cross arms at the base of the tube are attached severally: Volta's 

 electrometers with ivory scales, and sights for accurately determining the 

 angles of the deflection of the straws ; a Henley, or quadrant electrometer ; 



