754 ELECTRIC BELLS (669,670,672§| 1863-1882
669 Mahogany board 250 x 245, with bell in one corner, contacts
at two bottom corners, two coils in blue-covered wire. ~
Supplied by Funckler & Richards in 1863 for Dfl. 42.25,
together with the next bell.
670 Exacdy as 669, but with slightly larger bell.
672 Electric bell intended to hang on wall. Backboard 170 x 90;
diameter of bell 72. Electro-magnetics covered by box. Present
in Ven (1882a), no. 252.
754 754
Galvanometers
755 TANGENT GALVANOMETER J p g ' " 1883
Signed;, J.A. Scboonbeek HAARLEM
Baseboard 440 x 432; overall' height 462; outer diameter oMp
wheel 360
Mahogany baseboard, with brass plate bearing signature, three levelling
screws, and at right angles, another board bearing a mahogany annulus
bound with copper wire, green-covered. Inside is a circle of copper rod.
Six terminals at back, centre two marked RR, next two, 1, outside two,
2. The face of the dial is copper with silvered degree scale (internal diameter
200), numbered in quarters, and divided to 20 mins; dial is glass-
covered. Theire is a diamond-shaped steel magnet in the centre with an
aluminium pointer. Suspension of needle through glass tube with brass
mount above (broken). Brass pillar holds dial plate, which can rotate on
axis of pillar by rackwork. Said to represent the design of Jean Moth^e
Gaugain (1810-1880). See Gaugain (1853): “Tangentenbussole nach
einem neuen elektro-dynamischen Princip”. J.A. Schoonbeek, a
Haarlem instrument maker, was the amanuensis at Teyler’s Physical
Laboratory from 1878 to 1899, and it appears that this item cost Dfl.
53. He made the chemical balance 370.
756 GALVANOMETER (638) 18571
Signed: Ruhmkorffii Paris
Baseboard 652 x 331; overall height 664
Mahogany baseboard with four levelling screws, scale at top of upright,
glazed mahogany case, with backboard of light wood. At bottom of vertical
case are two oval coils of green-covered, insulated wire, wood and
brass mounted, with two terminals each side. Iron plate (22 x 140}
between the coils on a steel knife-edge. Above, pointer (length 435) of
non-magnetic, thin metal, possibly aluminium. At top of vertical board
is curved scale printed -in black on glazed paper, mounted on cardboard.
Inscribed in tens from 40 to 0 tp iO. Produced for class demonstrations.
Supplied in 1857 by Logeman & Funckler for Dfl..jl 24.30.
757 GALVANOMETER (639) before 1882
Unsigned; probably made in Haarlem
Base diameter 360; vertical board width 345; overall height
v j J j H
Round mahogany base, three levelling screws; above, horizontal ring of
brass with two terminals. Set vertically, mahogany board with paper
Seale 15 to 0 to 15lf|y ones. Pointer of mica (length 201) covered in
black paper, mounted on a steel bar with brass screws and counterweight,
and steel knife-edge which sits on a similar support.
758 GALVANOMETER (640) 1855
Signed: W.M. LOGEMAN HAARLEM.
Base diameter 155; overall height 307
Mahogany base, three levelling screws; glass dome, with oh inside a
wooden frame supporting two oval coils of wire covered in green silk.
On top is a brass,■'silvered ring (diameter 67) with a semi-circular scale
and the signature. Brass side-pillar supports magnetic needle and pointer
over scale 90° - 0° - 90° :by twos. Side lever with catch, outside
dome, frees pointer; also pair of wire contacts outside. Described by
Van Breda as: “galvanometer met 4000 windingen”; purchased for Dfl.
60.80 in,1855. Breda (li||9 )f 138.