Charles Wheatstone (1843): “An Account of several new
Instruments and Processes for determining the Constants of a Voltaic
Circuit”, 309, fig. 1; Wiedemann (1872), 232-234, fig. 81; Ganot
(1881), 870, § 945, fig. 842.
772 RESISTANCE BOX (630) 1882-1898
Unsigned; probably by Siemens & Halske, Berlin;
plaque inscribed: Neusilber regulirt [sic] bei 20 C. Stamped:
1536
Base 325 x 127; height of box 110
Set of resistance coils in a mahogany box with an ebonite top. Removal
of a key brings in a resistance of from 1 to 2000 Ohms. Ernecke [19051,
267, fig. 8420.
773 RESISTANCE BOX (1195) c. 1900
Base 71 x 54; height to top of box 44
Mahogany box with ebonite top; brass contacts; keys with ebonite finger
grips. Provides shunts of:
1, 1, I-
1 9 99
774 RHEOSTAT (1196) 1906
Signed: FERDINAND ERNECKE Hoflieferant Sr. Maj. des
Deutschen Kaisers BERLIN S.W. / Agent: J.C.Th. Marius, -
Utrecht.
Baseboard 710 x 160; back board height 335, width 658; overall
height 380
Mahogany baseboard with vertical board of black-stained wood. Three
dials marked: 1 ohm, 10 ohm, 100 ohm; ebonite handles and brass bars
to adjust onto connection studs. At back, three ebonite handles to tighten
FERDINAND ERNECKE
Hifllduaat Sr. Ml Ititi Untaten lUlicn
BERLIN S.W.
sAgBnli.lC,Th.Mnrlun,U trad ii,^
the contacts. A gliding contact runs along the top of the board, made
of ebonite with a copper contact bar screwed to it. Museum records this
as purchased in 1906.
775 AMMETER 1882
Signed: DEPREZBREGUETW* S.G.D.G. N° 273
Baseboard 265 x 155; magnet length 162, width 95
Double mahogany base with glazed lid; horseshoe magnet with coil and
needle at poles. Curved scale of silvered brass 42-0-42. Guide card in
glass lid: calibration to 46.7 amps. This and the voltmeter from the
same firm (776) were purchased in 1882 for Dfl. 65 each, most probably
for the experiments with tungsten filament lamps~(796, 797):.T
776 VOLTMETER 1882
Signed: DEPREZ BREGUET BF S.G.D.G. N° 145 ,
Baseboard 265 x 155; magnet length 162, width 95
Exactly as but calibration is to 61 volts. Purchased for Dfl. 65 in
1882, along with the ammeter.
VOLTMETER/AMMETER (1197fi c. 1900
Signed: Ferdinand Ernecke Berlin S.W. 46.
Agent: J.C.Th. MariuS Utrecht.
Base 190 x 88; height 190
Mahogany frame and baseboard, with three levelling screws; white enamel
scale reading to 3 volts and 3 amps; needle has air-brake.
Intended fë| class demonstrations, one or other scale may chosen.
BrncckclB905 , 275, fig. 8544; priced at 40 Mark.