124 THE MICROSCOPIC OUTFIT OF A TEXTILE 



Polarisation Apparatus. 



This is often extremely crude. Types which require the analyser 

 to be screwed on behind the objective, or in which the polariser 

 replaces the condenser, not only waste much time in making the 

 necessary changes, but the illumination is cut down badly. The 

 analyser should be built in the body tube, should be capable of 

 being swung or slid out when not required, and the analyser should 

 come below the condenser and should have the swing-out motion. 



Ultra-microscope. 



An efficient and easily handled form of ultra-microscope is urgently 

 required, not only for general scientific research, but also in several 

 branches of textile work, especially on the sizes and dyes. 



Fhotomicrograjjhic A pparatus. 



It is on this side that English apparatus is most defective. V/here 

 it is not a frank imitation of foreign types, it shows no evidence of 

 design as a whole, and in a number of small details is so defective 

 that I sometimes doubt if its makers have ever used it to take 

 photographs under the varied conditions that exist in a works 

 research laboratory. For my own purposes I desire an equipment 

 fulfilling the following conditions: — 



(1) As it will be used where there is considerable vibration, the 



mechanical design should be such as to reduce the effects 

 of this vibration to a minimum. That eliminates the type 

 where camera and microscope are on separate stands. 



(2) It should be easy to make a visual examination before the 



photograph is taken. This is most readily done by swinging 

 the optical system and microscope out of line with the 

 camera. It may be difficult when the light source is a 

 large arc surrounded by a lantern, but is comparatively 

 easy if a " Point.olite " set is used. I have found this 

 source most efficient and handy. It consists, as is well 

 known, of a tungsten arc in nitrogen; it burns for hours 

 witKout the slightest attention, and as the spectrum of 

 tungsten is exceptionally rich in the photographically active 

 rays, it is more powerful than a simple candle-power 

 measurement indicates. May I suggest to manufacturers 

 that before it is fixed on the optical train they should 

 discover in what direction it emits most light, and fix it 

 accordingly ? At present the direction used appears to 

 depend on other considerations altogether. 

 (3) It should be possible to pass from transmitted to vertical 

 illumination quickly and without having to make a number 

 of delicate adjustments. Among the unsatisfactory methods 

 at present put on the market I have come across the follow- 

 ing : — (a) Change the microscope to a vertical position and 

 use a vertical camera ; (b) swing the optical train through a 

 right angle round a vertical axis; (c) move the optical 

 bench parallel to itself and insert a mirror inclined to the 

 beam at 45°. The last is undoubtedly the method requiring 

 the least complication of apparatus if properly designed; 



