Several of our Swift microscopes are equipped with a Traviss mechanical Roller Stage. On the left side of the stage (shown on the right in the image), there is a single thin groove (blue arrow) into which fit the two wheels with thin tapering edges on that side of the apparatus. On the right side of the stage there is a double groove (red arrows), into which engage the horizontal flanges of a vertical axle controlled by a knurled knob beneath the stage. Turning this knob provides vertical or Y-axis movement of the apparatus on the stage. This vertical axle is contained in a little brass box which is hinged to the rest of the roller apparatus, and held firmly aginst its track by a strong spring (green arrow).

Horizontal or X-axis motion is initiated by turning a horizontally-orieinted second knurled knob, also on the right side of the roller attachment. This knob rotates an axle with two threaded worm-screw sections, separated by about 15 mm. These 2 worms engage with 2 gears which drive rubber-edged wheels below them. These rubber-edged wheels are held in contact with the slide holding the object being studied, and as they rotate, move the slide in the X-axis, right or left. The wheels are made of steel with brass edges and these brass edges are in turn edged with vulcanite rubber. Some other examples of this stage do not have brass between the steel and vulcanite. The slide is held firmly against these two wheels by a third wheel attached to a sprung arm which applies inward pressure from the front of the slide. See the video below for a demonstration of how the roller mechanical stage operates.

The roller stage attachment shown is signed: 358, J. SWIFT & SON LONDON PATENT 24345. 358 is apparently the serial number of the stage, as all roller stages I have seen have a different number. The other two in this collection are numbered 1289 and 1571. It should also be noted that these attachments were made in different sizes, to fit the different size stages on Swift microscopes. Number 1289 is wider than the other two so it can fit the wider stage of the Dick Petrographic Microscope. The Dick model also has (a second) simpler form of roller stage which acts more like a glide stage, moving forward or backward manually on the stage, motion of the slide in the X-axis being completely independent (this attachment has no rollers except on the sides of the stage).

The beauty of this attachment is how quickly it can be attached or removed, without any clamps or screws. It requires, of course, the stage already be pre-machined with the grooves on the right and left side, and to my knowledge, only Swift grooved the sides of their stages.

This device works well with some caveats. The stage must be smooth-polished with a thin coat of wax. Secondly the contacting edges of the two rubber-edged wheels must be free of any grease or they will slip and not move the slide. Third, the arm holding the top third wheel must be adjusted (by gently bending parts of it as needed), so that the wheel runs flat on the surface but without any downward pressure so its movement is not in any way restricted. I found museum wax satisfactory for reducing friction on the stage. The tracks on the sides of the stage and the rollers that contact it must also be free of grease. I found using methanol to clean all the contacting rubber edges as well as the stage sides and the contacting parts on the stage sides resulted in very satisfactory results, as shown here:

HISTORY:

This easily-attached accessory was invented in 1894 by Will R. Traviss, a Swift employee who became foreman. Traviss is famous not only for this stage attachment, but also for his later invention, the expanding stop for dark ground illumination. Although, as can be seen to the left, the original design of the roller stage had each of the two knobs on opposite sides of the stage, this was quickly changed to having the arrangement as shown on the examples on our microscopes, with both knobs on the same side, thus allowing one hand free to adjust the position of the slide in both directions.