THE SMITHSONIAN INSTITUTION. 



25 



against 

 issues, 

 opment 

 charges 



instruments for illustrating 

 wave motion; a large electri- 

 cal machine; Page's Electro- 

 Magnetic instrument, &c.^ 

 There is also in this room a 

 large Fresnel Lens, such as 

 is used in light-houses, and 

 various instruments for the 

 illustration of light, heat, 

 sound, dia-magnetism, etc. 



GERMAN STEAM ELEC- 

 TRICAL MACHINE. 



The Institution has just 

 imported from Carlsruhe, 

 Germany, a Hydro-elec- 

 tric machine which was 

 constructed by C. Eisenlohr 

 expressly to order. The 

 eflFects which can be pro- 

 duced by this machine, are 

 wonderful. 



It consists principally of 

 a tubular steam boiler rest- 

 ing upon glass columns, to 

 secure insulation. The 

 boiler is to be about two- 

 thirds filled with the purest 

 water, which is then heated, 

 and the pressure of steam 

 required is equal to six at- 

 mospheres. The steam at 

 this high pressure is allowed 

 to escape through very small 

 openings. The electricity is 

 thus produced by the friction 

 of the particles of water 



the inner surface of the orifices of the jet pieces, through which the steam 

 The least quantity of oil will destroy the friction, and prevent the devel- 



of electricity. This machine gives a constant succession of sparks, and 



a battery of sixteen large jars in thirty seconds. 



OEBMiiN STEAM ELECTRICAIi UACHINE. 



HARE'S ELECTRICAL MACHINE. 

 In the apparatus-room, the most prominent object is a large electrical machine 



