The Advanced Student's Petrological Microscope, c. 1908
Among the accessories are
a single eyepiece, a 1-inch and 1/4-inch objective each
with canister, a divisible substage condenser, and the
polarizing Nicol prism in a rotating calibrated mount.
The analyzer prism is within the tube held by a
slide-in mounting. The Bertrand lens is accommodated
within the tube using a focusing sliding-in
Extracted from the
Journal of the Royal Microscopical Society,
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.
The following was extracted from the 1914 Swift catalog:
This is the most universally adopted Petrological Microscope manufactured. It is in use in the majority of Geological Surveys and has been supplied, generally in large numbers, to practically every University, University College, Museum and Technical Institute, etc., in the United Kingdom and the Colonics, as well as to many in America and other countries.
The Coarse Adjustment is by diagonal Rack and Pinion. The Fine Adjustment is by a direct-acting Micrometer Screw the milled head of which is divided to read to .01 turn. A Differential Screw giving readings to .001 mm. can be lilted to order. The Rotating Stage, which is covered with dull black glass, is divided on the edge to 360° and reads by a vernier to 5°. Centring adjustments can be fitted. The Analyser is set in a brass box which slides in and out of the optic axis through the lower end of the body tube. The Prism can be made to rotate if desired. The Polariser has a divided flange and a spring catch to indicate when the prisms are crossed. It is mounted on an arm so that it can be swung out of the optic axis when not required. A Convergent System fits into a sleeve below the polariser. The top lens of this system may be removed if light of less convergence be desired. This optical system together with an Iris Diaphragm can be mounted independently on a swing-out Screw Focussing Adjustment. A Slot, which has a dust-proof cover, is cut through the body tube just below the analyser at 45" to the webs in the ocular. This slot is for the insertion of Wedges, Plates and other Compensators. A similar slot is cut through the ocular for the Micrometer and Compensators. A Bertrand Lens in a focussing mount is fitted through the upper end of the body. By this means the interference figures of crystals can be critically focussed and examined. When not required, the lens can be pushed out of the optic axis and the path of rays is left unobstructed. Immediately below the analyser is mounted another Bertrand lens which yields an extremely large interference figure; this lens also slides right out of the optic axis. The Ocular, which is supplied with the instrument, is cross-webbed and has an adjustable eye-lens; it is slotted to take a Micrometer and Compensators.
Within the case is a typed paper label reading: "This Swift petrological microscope number 14790 with accessories in the case belongs to and is the property of Angus Campbell Fraser". It is signed by his son F. J. Fraser with the date January 16, 1965.
Frank Jardine Fraser was
born in Wallasey, England on August 8, 1892. He was a
geologist living in Ottowa, Canada and was the author
of Geology of southern Saskatchewan, (Canada.
Geological Survey. Memoir, 176), 1935. His father
Angus, the original owner of the microscope, was born
in Gairloch, Scotland on June 11, 1844.