699
The apparatus comprises: a Leyden jar; an ‘exciter’, or small spark gap
in circuit from jar to coil; large ‘exciter’, or spark gap with ebonite handles
to adjust distance; glass tank filled with oil, containing a transformer,
its primary circuit attached to the discharge circuit of the
Leyden jar; the secondary circuit goes to the large exciter. A Ruhmkorff
coil is attached to terminals adjacent to the’Leyden jar. A plate hanging
below tfre large spark gap produces an electrostatic field to illuminate
Tesla or Geissler tubes.
699
Sundry equipmenBncludes: copper wire semi-circle holding
bulb (diameter 35); two Tesla tubes (length 100, diameter 55); a Tesla
tube with pips at each entkyno electrodes (length 905, diameter 16).
The booklet of November 1895 mentioned above, 698, is also relevant
here. Invoiced in April 1896 byMC. Th. Marius, Utrecht, for Dfl.
163.75, which probably included the induction coil above, 698. On
Marius, see Mooij (1988), 135-139.
Nikola Tesla (1856-1943), a Serbian, took up residence in the
United States in 1884, and worked on high frequency phenomena and
alternating current distribution. He invented his high frequency coil in
1891, and in February 1892 he delivered an invited Discourse at the Royal
Institution in London; Tesla (1893). Ducretet & Lejeune (1895), 9-10.
700 COMMUTATORS '(591,592,593) 3/4 19th C.
The commutator is both a contact key and current reverser. It is made
of a cylinder of wood or ivory the curved surface pardy covered by two
copper strips, alternating conducting surface with insulating surface.
Contact springs are in the electrical circuit. Developed by Ruhmkorff.
Deschanel (18f7j, j|63, fig. 548; S J iem in (1891), 394, fig. 259;
Ernecke [1905], 277, figs 8564, 8569.
5 !S | Mahogany base 90 xjBoverall height 70.
592 Simple change-over model; mahogany disc (diameter 7 |) with
crank and walnut handle; height 50.
593 Mahogany base 130 x 120; overall height 90. Handle moves in
a semi-circle between two copper contacts from terminals, j
Elias type. Acquired before 1859.
700 (5fW593, 5 f |) '
701 INTERRUPTER (588) before 1882
baseboard 100 x 70; diameter of disc 52
Mahogany board has two electric contacts, one with a rotatable brass
disc with handle on top, the other with a strip contact that presses
against the edge of the disc to make electric contact. Interruption is
effected through the 22 wooden dowels set into the edge of the disc. '