288 SEC. 10. ELECTJK1C1TY. 



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 Gourgon galvanometer ; a discharger, or spark 

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



Kew Committee of the Royal Society, Kew Observatory. 



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

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

 described in the British Association Report for 1 844. 



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 constantly 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 ; 

 a galvanometer, by Gourgon (the property of" Sir C. Wheatstone) ; a dis- 

 charger, or spark measurer ; and a Bennet's gold-leaf electroscope. 



Continued regular observations were made with these instruments for several 

 years. 



The wooden stand now exhibited was not the original table upon which 

 they were placed ; that, a fixture in the Observatory, having been destroyed. 



The Henley electrometer has also been replaced by a less perfect instru- 

 ment. 



1433. Spark Measurer, designed by Major Malcolm, R.E., to 

 show the striking distance of spark from tension exploders. 



School of Military Engineering, Chatham. 



1433a. Sheathed Electroscope. Prof. Beetz, Munich. 



1433b. Bifilar Electroscope, with copper and zinc con- 

 denser-plates for showing Volta's fundamental experiments, and 

 tourmaline for showing pyro-electricity. Prof. Bcetz, Munich. 



1434. Thomson's Divided Ring Electrometer and 

 Gauge, formerly in use for recording atmospheric electricity, at 

 the Kew Observatory. 



Kew Committee of the Royal Society, Kew Observatory. 



This instrument, which consists of two parts, the electrometer and the 

 gauge, was erected at the Kew Observatory in 1861, in connexion with a 

 photographic recording apparatus, and worked there for about four years, 



