BAIRD &.TATLOCK (LONDON) LTD. 



Description of Microscope No. 1374. See page 274 /or prices. 



This microscope is the outcome of a number of experiments undertaken to produce an instrument for metallo- 



ihic work at once simple and efficient. Messrs. Swift & Son believe the design to be the most convenient yet 

 otiered to Metallurgists, Engineers, and others whose work necessitates the examination of the microscopical 

 structure of metals and alloys. 



The base of the microscope is a strong and heavy horseshoe tripod on which the instrument is exceptionally 

 well balanced. 



The optical tube is carried by a strong crane arm which gives great firmness and steadiness to the whole body 

 under the highest magnifications. The shape of the arm also makes the microscope one which is very easily 

 handled. 



The body is moved in a solid fitting similar to that adopted by Continental makers, with the spiral rack and 

 pinion originally patented by the firm of James Swift & Son. 



The rectangular stage is large and very strong and steady. It is fitted with quick and slow focussing move- 

 ments. The quick adjustment is by spiral rack and pinion worked by the milled head (F) shown in the figure. 

 The slow movement to the stage is obtained by the firm's modification of their well-known lever fine adjustment. 

 The milled head (E) for putting this in action is on the same shaft as that of the rack motion. By this arrangement 

 the greatest convenience is secured as there is no need to shift the hand from one part of the instrument to another 

 in changing from rapid to slow focussing. 



The application of a strong, steady, and yet delicate fine adjustment of the stage, instead of to the optical 

 tube, is practically a necessity in an instrument designed for the examination of opaque substances under vertical 

 illumination. The stage, as shown in the figure, is solid, but it can be made with an opening, and supplied with a 

 chuck fixed to its under surface so that pieces of rod, etc., may be rapidly adjusted for examination. 



The illuminator is entirely novel In Its construction. It possesses several new features^which distinguish it from 

 any form of vertical illuminator which has yet been fitted to microscopes for metallographic work. The arrange- 

 ment of its constituent parts will be understood by reference to the figure. It is detachable as a whole from the 

 body tube at (A), so that small photographic lenses may be used when it is desired to obtain a general picture of a 

 large lield. (B) is a milled head for adjusting the angle of the reflector, which consists of a rectangular plate of 

 glass with surfaces worked optically flat and parallel. All chance of any distortion of the image by the reflector is 

 thus prevented. 



The smaller milled head (c) is the end of a short fitting which passes through (B) and carries small circular stops 

 of various sizes. These are designed to cut out reflections from the lenses of the object glasses. When dealing 

 with bright polished metallic surfaces they are seldom necessary, as the light reflected from such objects sufficiently 

 overcomes that thrown back from the glass surfaces of the lenses. In the case of dull etched surfaces, however, 

 the stops will be found very useful to prevent a general haziness over the image, and to ensure an illumination which 

 will give photographs with clear contrasts. (D) is a handle for moving an Iris diaphragm which works above the 

 reflector, and which will often be found necessary for reducing the aperture of an objective, for cutting off any stray 

 reflections, or for increasing the apparent depth of focus when photographing somewhat uneven surfaces. 



The whole illuminator can be rotated, round the vertical axis of the microscope, so that the source of light can be 

 placed at the side of the instrument, in front of it, or at any point between these positions. The opening for admit- 

 ting light to the reflector is of sufficient size to clear the aperture of the largest back lens of any objective made. 

 No diaphragm or stop is fitted to this opening, as all modifications in the size or shape of the beam of light thrown on 

 to the reflector should be made by a diaphragm placed close to the radiant source itself, which, when properly 

 adjusted, should be in the same optical focus as the object to be examined. This is effected by making the distance 

 from the radiant to the reflector equal to that from the reflector to eye-lens of the ocular, or to the diaphragm of the 

 ocular if it is of the positive form. It will be seen from this description that the vertical illuminator contains all 

 that is required to secure perfect illumination, and absence of all false light, together with the greatest freedom 

 of adjustment and manipulation, and that the various parts are arranged in a compact form of great strength and 

 steadiness. Messrs. Swift & Son believe that this new illuminator will give the best results obtainable in the 

 examination and photography of metallic and other surfaces where vertical illumination has to be employed. It 

 should be used with objectives properly corrected for uncovered objects, as supplied by Messrs. J. Swift & Son 

 for use with this instrument. If desired, however, a screw adjustment could be fitted to any of their high-power 

 objectives for use with covered or uncovered objects. 



JAMES SWIFT & SON'S 

 "Universal," " I.M.S.," "Research," and "Army" Microscopes. 



These four instruments, which have only recently been introduced, form the finest and most comprehensive 

 series of Microscopes yet constructed. Usually they are mounted on massive claw tripods, as illustrated, but 

 a horse-shoe foot can be substituted at the same cost. They incline to the horizontal, in which position they are 

 accurately stopped. The limbs, which are shaped to form a handle for carrying, are milled out of extremely 

 hard phosphor bronze castings, and all bearings are ground and fitted solid. 



Coarse Adjustment by diagonal rack and pinion on a solid milled and ground in slide. 



Fine Adjustment by Swift's " Improved Climax " vertical lever, which was introduced and patented by them 

 over thirty-five years ago, and which has recently been widely copied. With this adjustment loss of time or back- 

 lash on reversing the action is absolutely impossible, moreover, there is practically no chance of either the cover 

 glass or objective being injured through careless focussing. The adjustment is operated by two milled heads, one 

 on each side of the limb ; one of these carries a divided drum, one division of which corresponds to a movement 

 of the tube of .001 mm. As the entire adjustment is contained in a cavity milled out of the limb, there is no liability 

 to injury through dust or reagents reaching the working parts. 



The Draw Tube, which is nickelled, is divided and figured in millimetres. 



The Substage, which carries the regular Abbe condenser with iris diaphragm and stop carrier, is focussed by a 

 rack and pinion. The optical part can be swung right out of the optic axis. As it is held central by a spring catch, 

 it can instantly be brought back to that position with absolute truth. As they are unnecessary with an ordinary 

 Abbe condenser, centring screws are not provided, but they will be fitted without any extra charge should they 

 be desired. 



See pages 276 and 277 for prices ot above Microscopes. 



ICHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



275 



