Extracted from the
Journal of the Royal Microscopical Society,
1907
This Microscope has
recently been further improved from suggestions of J.S.
Flett. The coarse adjustment is by means of patented
spiral rack and pinion the slow focusing adjustment by
a millimetre screw the milled head of which is divided
to read to 1/120 mm The glass covered revolving stage
has the edge divided to 360 reading to 5 by means of a
vernier The polariser is fitted with divided flange and
spring catch to indicate the crossing of the Nicol
prisms and is made to throw out of the optic axis when
required immediately above the polariser is fitted the
convergent system of lenses The analysing prism is
fitted in a metal box which slides into the optical
tube below this is cut an opening for the introduction
of a quartz wedge undulation plate or gypsum plate
Above the analysing prism is fitted a Bertrand lens
with telescopic adjustment by means of which the
interference figures are perfectly shown in thick or
thin crystals The tube of the cross webbed eye piece is
provided with an opening to allow of the use of a
quartz wedge or micrometer.