The Microscope. Its History, Construction, and Application 15th ed. / Being a familiar introduction to the use of the instrument, and the study of microscopical science

by Jabez Hogg

Messrs. Swift’s Microscopes.

Messrs. Swift’s Microscopes have a well-established reputation for quality and good workmanship, and therefore can in no way suffer by comparison when placed beside those of other opticians. One of the characteristics of Messrs. Swift’s microscopes—and this runs through the whole series—is that they are all made to a standard gauge, so that the several parts of the instruments, as well as their accessories, are interchangeable; the cheaper forms, with those of the first quality and finish. Should the student, then, start with a No. 1 model, he can at any time build it up, as it were, with the accessories designed for a No. 3 or 4, that is, for an instrument of double the price he started with. The optical centre is preserved throughout the whole series of microscopes.

Fig. 81.—Swinging Leg Attachment of Swift & Son’s Four-Legged Microscope Stand.

The tripod foot has, it appears, taken the place of some of their other forms of instruments, while their four-legged tripod, if it can be so designated, is a novelty of quite an unusual character.

The swing leg is attached to the framework of the tripod by the screw (Fig. A), which is provided with a powerful steel spiral spring, compressed between two steel collets when the screw is driven home, as shown in Fig. B.

The expansion of this spring will obviously take up and compensate automatically any wear and tear that is likely to occur between the bearing surfaces, and it is therefore impossible for the fitting to get loose.

Swift’s Four-legged Microscope ([Fig. 80]) is one possessing great stability in whatever position it may be placed; the body being supported on a horse-shoe platform, from which its four legs spring, the two front legs being fixed, while the hind legs are pivoted to the platform. This arrangement of pivoting the hind legs enables the microscope to adapt itself to any uneven surface, thus keeping it always in a steady position, while it also reduces the danger of being upset by any lateral movement of an accidental nature. The feet are studded with corks, an additional aid to steadiness and fixity for microphotography. The length of the body from the ocular to the nose-piece is 6½ inches, and can be extended to 9 or 10 inches by means of the draw-tube, which has a millimetre graduation. The stage, which is of horse-shoe shape, is provided with spring clips, to which a movable mechanical stage can at any time be attached. The sub-stage partakes of two forms, one being an ordinary fitting, taking an ordinary condenser; the other, the regular rack and pinion achromatic condenser with centring adjustments. It has a diagonal rack and pinion coarse adjustment, the fine adjustment being made by micrometer screw of the finest character.

Fig. 82.—Swift’s Spiral Rack and Pinion Coarse Adjustment.

[Fig. 82] is intended to illustrate the advantage of the spiral rack and pinion which Messrs. Swift fit to their microscopes, in place of the ordinary conventional horizontal rack and pinion movement. The advantage will at once be seen, since there is more gearing contact between rack and pinion, thus ensuring durability and reducing loss of time or back lash to a minimum, with less wear and tear. The leaves of the pinion also roll into the teeth of the rack by degrees, ensuring a very much smoother action, which, if properly made and fitted, prevents the gearing of the two being felt by the hand whilst focussing.

Fig. 83.—Graduated Supplementary Draw-Tube.

[Fig. 83] is a supplementary draw-tube with rack and pinion movement, which can be adapted to any of Swift’s microscopes in place of the ordinary draw-tube, the size of the thread being of the same diameter, so as to render all draw-tubes, as well as other parts of these instruments, interchangeable. The draw-tube being divided into millimetres can be extended from 160 to 250 millimetres. One advantage of this arrangement is that the correct adjustment of any objective with each eye-piece is easily found and recorded for future observations with the same combination.

Messrs. Swift’s Three-legged Tripod Microscope ([Fig. 86]). In most respects the description already given of the four-legged instrument is applicable to this stand. Although of an apparently different form, it can be built up, as already explained, into one of a higher class. It is suitable in every way for histological investigations. The horse-shoe platform in this, as in the preceding stand, is extremely serviceable, as it allows the pillar of the instrument to rest firmly upon it, thus rendering the stand very rigid.

Swift’s Bacteriological Microscope ([Fig. 84]), designed by Professor Wright, of the Army Medical School, Netley, a sufficient warranty of its excellency and perfect adaptation for bacteriological high-class work. One of the advantages connected with this microscope is the facility with which it can be adapted for either high or low power investigation, without the necessity of adding or detaching any part. The objectives, arranged on a triple nose-piece, are approximately in focus when revolved into position for immediate use, thus effecting a saving of time in changing the objective. Moreover, the nose-piece carrying the objectives is of new construction, and fitted in such a way that the entry of dust is rendered impossible.

Fig. 84.—Swift’s Army Bacteriological Microscope.

Fig. 85. Under-Stage of same.

The Abbe condenser, fitted with an iris diaphragm, is mounted on an eccentric arm, so that it can readily be thrown out of the axis of the microscope when not required, without having to re-arrange the focus when again brought into position. The condenser must be turned aside when plate cultivations and preparations of unstained bacteria are being looked over for selection of colonies for mounting, in which case an arm carrying a quadrant with three apertures is brought into position in place of the condenser, the apertures being severally centred by a spring catch and used with oblique light. This arrangement, shown in [Fig. 85], is seen from the under surface of the stage. The stage is sufficiently large, so that when Petrie plates are being examined at the extreme edges there is little fear of their overbalancing.

Fig. 86.—Swift’s Histological Students’ Microscope.

The fine adjustment is the Swift’s Patent Campbell Differential Screw, which offers great facilities for delicate focussing with the highest power objectives. The stand is of the most substantial and rigid form, and thus ensures the microscope from vibration.

The under-stage of microscope ([Fig. 85]) is seen to be of the most approved form.

Fig. 87.—Swift’s Advanced Students’ Microscope.

Swift’s Advanced Students’ Microscope.—In this microscope ([Fig. 87]) we have a superior instrument for the use of the advanced student, which may be described as of high mechanical excellence, well suited for every requirement of work. The stand is the well-known tripod form of their Challenger Microscope, and admits of the instrument being placed at any angle of inclination; the body is short enough to work with objectives of Continental makers, and is provided with a draw-tube, to elongate it to the standard of 10 inches, with a diameter of 1³⁄₁₆ inch to take the same eye-pieces as the larger stands. The coarse adjustment is by spiral rack and pinion; the fine, by a carefully made differential screw motion for delicate focussing. The stage is of the horse-shoe pattern, to which a mechanical stage can at any time be adapted, as well as an achromatic condenser to the sub-stage seen beneath. Here the student will find the foundation for a superior instrument.