651
attached to heavy, L-shaped iron frames with brass blocks that fit into
slots on the base frame and are fixed in any required separation by brass
butterfly nuts underneath. The iron base frame has four brass legs and,
in the centre, a brass bracket for attachments. The two iron armatures
which can be screwed on or off the inner ends of the cylinders have the
form of rounded cones, and produce a great concentration of magnetic
force at their extremities. The accessory supporting bar, with a measuring
scale, is now missing. A bracket that fits on top of this bar is present,
as is the brass supporting frame to suspend different specimens. Frame
width 115, overall length 334. There are two other supports, both in
the form of candle-holders, with sliding adjusters inside to push out
candle; one has remain's of candle in place. Also present: a glass cell for
liquid, between black-lacquered plates, with cork bung. Cell 58 long;
diameter 27.
If the outer end discs of the coils are removed, there areRter-
native attachments: disc (diameter 160) with Silvered degree^spale-
marked 0 - 90 in quarters; into this fits eyepiece, with nicol prism with
vernier, 10-0-10 by ones. The vernier Is signed: Ruhmkorjf à Paris. At
other end a nicol prism polarizer screws' ifanAlso present: transparent
non-birefringent plate (diameter 45), with brass rim with a circumferential
cut so that it can be wired for suspension; frame stamped: 2 .
Also paper twist with seven round-headed wood screws, and six countersunk
wood screws. Referred to in the Annual Reports for 18»-75.
Used for experiments following Faraday (see 650) into diamagnetism
and paramagnetism, and for influence1 of magnetism on
crystalline materials, and influence of magnetism on the level of polarization
in light rays. For an extensive account, see Guillemil|(1891),
363-372, fig. 2 4 4 # ||8 , fig. 303rmore briefly Deschanel (1877), 638-
641, § 504, fig. 432. RuhmkorfFs magnets and va’rious pole pieces are
■ustrated in M. Pouillet, Éléments de physique, 7th edn (Paris, 1856),
table 25. On Ruhmkorff, Brenni (IV).
List o f Specimens
Original sheet is signed by J.A. Schoonbeek.
0 = cobalt (missing)
1 = bismuth bar
2 = tin bar
3 = nickel bar
4 - zinc bar
5 = iron small rod
6 - sulphur 2 sticks with ink number
boxwood bar
8 = oak bar
9 = mahogany bar
10 - pith bar combined with wood.
11 - beech bar
12S|= ebony bar
Average length 50, section 11, all stamped with their numbers and
hooked, except sulphur sticks. Sundry other items not classified.
§ 38. Elee man ts, Eclaii'agtì éleclrìquc
(Télég’^aphes, Hoi*log,cs, eie.)
.‘1800. A p p a r e i l e i e F a p i i d a y , pour rópèter Ics experiences sur In poln-
risnlion, lo raiignólismc e t Je dinmngnétisnie des corps solides el liqui-
651 Geneva (1913), 62
652 MAGNETS (448,450-462, 844, 916-921, 925) 4/4 19th C.
The majority are single or triple lamellar horseshoe magnets with keepers.
Many are signed with a punch: GEM VAN WETTEREN; they also bear
a number, which is also on the keeper. Some are contained in their original
box. Those that are not signed may have been made by Van Wetteren. In the
following listing, each item is identified by the Teyler’s Museum number as
given in Ven (1898)...Inventory numbers 448-462 were acquired before
1882.
448 Van Wetteren, N. 3059; 265 x 120.