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 mounting.
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.
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.
