269
brass forceps; two glass fish tubes, length 95, diameter 11; brass objective mount
with six lenses set in line. The barrel' of the microscope may be removed from the
plate and a brass ring substituted, which carries in a llot a bar with five circular
apertures (4 to 10) and one slit aperture (t x 11 for experiments with prisms.
Van Marum records, on 21 September, 1790, the payment of ƒ 63 to Paauw of
Leyden for a solar microscope. The woodewcase is covered on th® outside with black
fishskin, and inside with green velvet; its appearance suggests a date rather earlier
than 1790, but it is not impossible that it continued to be held in stock. George
Adams Snr in his book Micrographia Illustrata shows a solar microscope rather like the
one described above, but it must be remembered that all retailers sold this type of
instrument, and they were probably produced in quantity by only a few workshops
for the whole trade. In his Inventory Van Marum has left the provenance blank:
“ Een Zon-microscoop door... in een segreine kisri^*«
Adams (1771) pp. vi-x, III.
Inv. 6g/4
269 LUCERNAL MICROSCOPE 1789 (J63) Fig. 235
By George Adams, London
Overall height 495, length of support bar 475, projection box length 4 » area at
viewing end 172 x 172; accessory box 325 x 169 x 87.
The flat, brass, fixed tripod foot supports a pillar and a stay on which is fixed the
mounting for a stout bar, which can be racked to and fro for focusing. Above is
fixed a pyramidal projection box, which carries at one end the collar to which the
objective lens mounts are screwed, and at the wide end, in slots, a large double convex
lens, diameter 130, focal length 210, and a ground glass viewing screen. Finally a
square of wood can be slid in to protect the glass when not in use. Below and
beyond the screen is a brass tube that carries the eye-locating aperture (this is a
replacement, made in 1943, after the illustration in Adams, EssajjSL At the front
of the bar is attached the specimen-holding stage. The one for transparent objects is
a spring stage, with a condensing lens, diameter 59. It may be replaced by a stage
for opaque objects, which entails the object being strongly illuminated. For this
purpose, the bar carries a bulls-eye lens, diameter 59, and a concave mirror, diameter
60. The mahogany accessory box contains a selection of transparent objects in six
boxwood sliders, and four trays of opaque objects, each tray with four slides. There
.|lre seven objective lenses in mounts, two long-focus lenses in mounts, and an ivory
talc box, containing mica disks and brass wires for preparing slides. The pair of long-
focus lenses may have been the two lenses for the English microscope referred to by
Van Marum in his 1793 list of minor purchases. For them he paid, in the September,
ƒ 18 to the German optician Oppelt.
The image of the objects may be viewed without the ground glass screen by putting
the eye up to the aperture intended to locate it in the right position. If there is
sufficient light, then the screen may be used, in which case the image is more generally
viewable (as with a television set), or its outline can be drawn. In fact, Adams says
that all the engravings of microscopic objects made for his Essays were taken from
lucernal drawings. Adams shows an Argand lamp (see Cat. 344) in use with the
lucernal, for, as he says, it is the most suitable for microscopy “ on account of the
clearness, the intensity, and the steadiness c|i; the light” . These lamps, Adams says, are
sold by Mr. Parker. Adams’ catalogue, bound in with his Essays, gives the price of a
lucernal microscope as£ 21. He declares that: “ This microscope was originally thought
of, and in part executed, by my father [died 177JP; I have, however, so improved and
altered it, both in construction and form, as to render it altogether a different instrument.
The approbation it has received from the most experienced microscopic observers, as
well as the great demand I have had for them, has fully repaid my pains and expenses,
in bringing it to it’s present; state of perfection.”
On 3 November, 1788; Van Marum wrote to Magellan in London to ask him to
order from Adams a lucernal microscope with “lanthorn” and lamp to project images
of transparent objects^ together with the instrument for cutting thin sections of wood
(MV). A letter from Magellan to Van MarifHof 30 December, 1788, says that the
price of the Adams lucernal microscope will now be six guineas more than the twenty
gfjlineas quoted. In a letter of 30 June, 1789, to Van Marum, Adams apologises for
the delay in sending the lucernal microscfepe, due in part to the illness of Magellan,
and refers to “ a lanthorn and cutting engine” . The microscope and accessories were
finally despatched in September 1789 (letter of Adams to Van Marum, 30 September,
I78gBTheir arrival was noted by Van Marum on 23 November, 1789, and he lists
the ccTsts as: lucernal microscope, lanthorn, etc. £ 25-10-0; cutting knife £ 6; box
for the latter 4s.; shipping 10s; total 32-9-0 |.«cj.
Adamsffli78S 65—8.0, III: Disney (1928) i86fHXL A36; Carvalho (1951) 251 f.
See also Cat.'272.
Inv-
270 COMPOUND MICROSCOPE 1808 (368) Fig. 236, 237
By Harmanus van Deijl, Amsterdam
Signg|f on 8 p barrel: Harmf van Deijl Inv: et fecit Amsterdam
Overall height closed 353, radius of foot 80, barrel length closed 170, diameter 38;
box 260 x 230 x 93.
The stand is that of a typical, inexpensive microscope of the late 18th century. The
flat, folding tripod; has a bevelled shoe into which slides the square-sectioned pillar, in
the centre of which is cut a rack so that the stage may be raised or lowered by a
pinion. At the top of the pillar is a small drum with a slot to take the objective bar,
held in place by a spring, so that it can be moved in any direction by hand for the
so-called aquatic movement. The objectives screw in a ring at the end of this bar,
and they may be used with the_compound barrel or without, as a simple microscope.
The stage has a large circular opening to take a Bonnani spring stage or a watch
glass. On either side are wings with a small hole for the fish plate and the above-
stage condenser. Fitted to the front leg is a concave mirror, aperture 45. The stand
is unsuitable for the heavy barrel, which when in place makes the instrument unstable,
particularly when the draw tube is extended to increase the magnification.