THE MICROSCOPIC OUTFIT OF A TEXTILE RESEARCH 



LABORATORY. 



By R. S. Willows, M.A., D.Sc. 



In the interests of brevity I will confine my remarks closely to 

 the requirements of a research worker in the textile industry. The 

 materials to be examined are fabrics, yarns, fibres, starches, and 



Objectives. 



The objectives used will be from 2 in. down to an oil immersion, 

 and for certain purposes an ultra-microscope of the cardioid or 

 similar type, while for special work an immersion ultra-microscope 

 may be a great advantage. The most useful lenses are the 16 mm., 

 the 6 mm., and in a less degree the 4 mm. and an oil immersion. 

 The first is most useful for examining single fibres, while the second 

 will do most of the routine work on sections, especially if it will 

 stand a high power eye-piece. Strange to say, at least one English 

 maker of high-class lenses does not produce a 6 mm. lens. I have 

 found certain English apochromats excellent in flatness of field and 

 definition, but they have the disadvantage of a short working 

 distance ; it is fair to add that in the last respect they are no worse 

 than Continental types. For most purposes I find some semi- 

 apochromats in my possession are all that is required ; the field is 

 not very flat, but the definition in the centre is excellent, their 

 working distance is large, they will stand an x 18 eye-piece, and 

 they are comparatively inexpensive. 



Stands. 



1 prefer the English type of stand to the Continental model, 

 on account of the better distribution of weight and consequent 

 greater stability, and also for the greater space for the substage. 

 The tube must rack out to take a 2 in. objective, and in this 

 connection it is a great advantage if the stage can also be racked. 

 The latter movement is also very useful w^hen it is required to use 

 vertical illumination. A mechanical stage, centering substage, and 

 high-class condenser are taken for granted, even on the simplest 

 types of stand. Very frequently a considerable portion of the slide 

 has to be examined ; this should be possible without fouling the 

 condenser. 



As the material to be examined has frequently to be submitted 

 to the action of acids and alkalis while it is on the stage, the latter 

 should be made of a suitable material, and should be designed so 

 as to eliminate as far as possible the chance of injury to the 

 instrument. Apart from material used, the design of such a stage 

 appears to have received little attention. It is in such examinations 

 that a large working distance for the objective is so markedly 

 advantageous. 



