| The de la Rive tube is used to demonstrate that
the lighted streamers appearing in a Geissler
tube are actually streams of charged particles. The apparatus is essentially
an electric egg with a soft-iron
core placed lengthwise through it. This rod is magnetized by an electromagnet,
as shown in the diagram at the right, drawn from a Ducretet catalogue.
The streamers of light travel in a rotating helix from one high voltage terminal to the other, the direction of the helix depending on the direction of the magnetic field.
The Dartmouth apparatus was made by Apps of London.
The instrument from St. Peter's College in Maynooth, Ireland, was made by George Yeates & Son of Dublin, ca, 1864, and has an electromagnet inside the tube.
The Hampden-Sydney tube, as well as the apparatus offered for sale at an eBay auction in 2001, were made by Ducretet of Paris. The Colorado tube was make by Ernicke of Berlin.
University of Colorado
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