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MAKER: JAMES SWIFT & SON

MODEL: 'BACTERIOLOGICAL' MICROSCOPE WITH OPTIONAL TRAVIS 'ROLLER STAGE'

c. 1902

SIGNED: J. SWIFT & SON, LONDON

SERIAL NUMBER: 11200

DESCRIPTION HISTORY

Please Click On Any Picture for a Larger Version

DESCRIPTION:swift bacterial understage This microscope arises on an an 'English' or 'Crouch' foot with a U-shape in the rear forming the third toe of a tripod. It is signed on the bottom of the rear of the foot 'J. SWIFT & SON, LONDON.'   The foot and limb have an oxidized brass finish. Course focus is by diagonal rack and spiral pinion, as invented by Swift. Fine focus is by micrometer screw long lever. The tension on the fine focus screw is adjustable via a small knurled knob projecting backwards on the limb just below the fine focus wheel. The fine focus has a small diameter knurling in the center for fast movement, and the usual larger diameter wheel for finer movements. The stage is covered with vulcanite (hard rubber) and has a registration scale in the upper right corner just like the 'Histological and Physiological' model in this collection. There are lacquered brass screws for adjusting tension on the inclination joints and also the rack and pinion slide. The substage mirror is plano and concave and is on a gimbal. The mirror gimbal is attached to a sleeve riding on the chromed tailpiece. An Abbe condenser with iris diaphragm is focused up or down by spiral screw and can be turned aside out of the optical axis when in its lowest position. There are three Swift objectives, being of 2/3, 1/6, and 1/12 inch focal lengths, the latter an oil immersion. The n.a. is 1.30 for the 1/12 inch, and 0.83 for the 1/6 objectives.

This microscope is equipped with a Travis mechanical 'Roller Stage'. The device rides on wheels in grooves machined into the right and left edges of the stage. On the left side there is a single thin groove; on the right there is a double groove. The Travis attachment has two wheels with thin tapering edges on the left side, and a small diameter double-grooved wheel on the right controlled by a knurled knob. The box holding the double grooved wheel is hinged to the rest of the attachment and the this small wheel is held firmly against its track by a strong spring. This supplies the 'vertical' or X-axis motion to the slide. 'Horizontal' or Y-axis motion is accomplished by 2 vulcanite wheels in direct contact with the edge of the slide closest to the limb, while the upper edge is pressed towards those two wheels by a third vulcanite wheel on a sprung arm. The driving wheels have pinions driven by worm screws both attached to a single thin axle driven by a knurled knob. This attachment is signed: '1571, J SWIFT & SON LONDON PATENT 24345. 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.



HISTORY OF THE BACTERIOLOGICAL SWIFT MICROSCOPE AND THE TRAVIS ROLLER STAGE

crookshankThe Bacteriological Swift microscope was introduced in its earliest form in 1887 as reported in the JRMS for that year on page 801. The microscope was said be brought out on the suggestion of Professor Dr E. M. Crookshank, a famous bacteriologist. It featured a slotted (and therefore U-shaped) stage, a high-angle Abbe condenser, a glass stage surface and importantly a lever modification of the Bausch & Lomb continental parallel spring fine focus mechanism. It should be noted that this model had a rack and pinion focusing to the substage and glass covering to the stage, both of which changed with the next variation in the model.

 

bacterial By 1901, Swift was advertising this microscope as seen here with a solid stage, and now covered in hard rubber, the purpose of which was to keep warm subjects from cooling off too quickly. Now the substage fine focus was changed to the (less expensive) type seen on this and many other microscopes during this time period and for a long time afterward. This type of vertical screw fine adjustment was popular among German and American Makers for many years afterwards. An engraving of this microscope thus appeared in Emery's 'Handbook of Bacterial Diagnosis for Practioners' of 1902. You will note that this is the exact model pictured on this web page, even including the triple nosepiece changer.

 

bacterial By 1904, the design was again altered, as it was on some other Swift stands, most notably the 'Discovery' model, to incorporate a simpler and cheaper continental style fine focus. The stand was otherwise the same.

 

rollerstage This microscope is equipped with a Traviss mechanical 'Roller Stage'. 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 the original design of the roller stage had the two knobs on opposite sides of the stage, this was quickly changed to having the arrangement as shown on this instrument, with both knobs on the same side, thus allowing one hand free to adjust the focus, etc.

 

Swift with engraving