324 SEC. 10. ELECTRICITY. 



in protecting buildings said to be the first model of the kind, 

 and to have been made by Dr. PRIESTLEY with his own hands. 



Conrad Wm. Cookc, M. Soc. T.E. 



1383. Old Electric Egg (beginning of last century). The 

 property of Prince Pless. The Breslau Committee. 



The great age of the instrument appears both from tradition and from 

 the style of the wooden frame and the nature of the brass work. It is certainly 

 one of the oldest instruments of the kind. 



1384. Apparatus employed by Sir Charles Wheats tone to 

 determine the Velocity and Duration of the Electric Dis- 

 charge. 



Rotating mirror. Spark disc. Early rotating disc with balls 

 and sliding rod. The Council of King's College, London. 



1385. Riess* Spark Micrometer. F. Rob. Voss> Berlin. 



1386. Apparatus for testing Lightning Conductors. 



M. Th. Edelmann, Munich. 



1387. Electrograph, for the production of electric sand- 

 figures, constructed, from the plan of the exhibitor, by M. Th. 

 Edelmann. Prof- W. von Bezold, Munich. 



This serves for the study of the nature of the electric discharge in simple 

 or branched circuits, with the aid of sand-figures. The figures exhibited have 

 partly been produced with this apparatus, partly under the air pump, and by 

 means of a caoutchouc solution transferred from the ebonite plate to black 

 tissue-paper. They are accordingly not copies, but true originals, produced by 

 the discharge. 



1388. Framed Table, with electric sand-figures. 



Prof. W. von Bezold, Munich. 



VL APPARATUS FOR PRODUCING AND OBSERV- 

 ING EFFECTS OF CONTINUOUS ELECTRIC 

 CURRENTS. 



a. HEATING AND LUMINOUS EFFECTS. 



1389. Diagram showing the Amounts of the Electro-motive 

 Force, and the Peltier and Thomson Effects in a Thermo- 

 electric Circuit of Iron-Copper, both junctions being at 

 temperatures under the neutral point. For teaching purposes. 



Prof. Tait. 



1390. Peltier's Apparatus, for studying the thermal effects 

 of currents in circuits composed of two or more metals. 



Conservatoire des Arts et Metiers, Paris. 



