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C. U. C. p. ALUMNI JOURNAL 



scope differs from the familiar type of 

 instrument in that the ilkiminating ap- 

 paratus is not mounted below the stage 

 for as the objects to be examined are in 

 almost all cases opaque, it is necessary 

 to employ vertical or overhead illumina- 

 tion. The latter is accomplishel by hav- 

 ing a mirror or prism set in the objective 

 in such a manner that it will reflect 

 downward through the lens combination, 

 a pencil of light admitted by an aperture 

 in the tube of the objective. The mirror 

 or prism is either placed out of the line 

 of vision or is perforated so that the 

 light rays are not intercepted. An arc 

 with a condensing lens is usually em- 

 ployed as the illuminant. Preparation 

 of objects for examination involves the 

 grinding and polishing of the specimen 

 to obtain a perfectly plane or level sur- 

 face. Where differential effects are de- 

 sired, objects are subjected to the action 

 of etching media which, by dift'ering in 

 action upon the constituents of the 

 specimen, may give information as to its 

 chemical composition. In more modern 

 types of microscopes designed for this 

 branch the instrument is reversed, the 

 objectives being below the stage, the ob- 

 ject being placed on the upper surface of 

 the latter. Coarse focussing is performed 

 by moving the stage instead of the body- 

 tube. This placing of parts has the 

 advantages of permitting the use of 

 specimens of any size with but one side 

 ground and obviates the moving of the 

 source of illumination for each specimen. 



Utilization of the microscope in this 

 field furnishes information which, if not 

 as accurate as that resulting from chem- 

 ical tests, has the great advantage of 

 being quickly obtainable. I have been 

 informed that the instrument is being 



extensively used in the iron and steel in- 

 dustries for the examination of castings 

 and alloys. 



Textiles and Papers. 



The microscope in a simple form 

 (linen testing lens) has long been em- 

 ployed in textile industries. In this field 

 where the main requirements are identi- 

 fication and approximate quantitative 

 estimation of the different fibers used in 

 fabrics, it furnishes the desired informa- 

 tion quicker and more satisfactorily than 

 any other means. Its use has been ex- 

 tended to the fur manufactures, and 

 although some of the sophistications 

 practised in this business are almost im- 

 possible of detection by eross methods, 

 even by experienced persons, microscopic 

 examination is simple and furnishes re- 

 liable information. The various textile 

 fibers and hairs show greater or less 

 differences in histologic structure so that 

 the procedure is but one of comparison 

 was authentic samples. This is one of 

 the simplest branches of microscopy be 

 cause we are dealing with but one type of 

 tissue instead of the many found in drug 

 and pathological examinations. Micro- 

 scopic examination of fibers used as 

 paper material is a little more difficult, 

 as such material usually consists of more 

 than one kind of fiber together with 

 mineral matter or a filler. But macera- 

 tion of the material followed by examina- 

 tion of the pulp usually yields consider- 

 able information about the substances 

 employed. 



The examination of textiles is per- 

 formed by teasing out both the warp 

 and woof material followed by direct 

 observation with objectives of moderate 

 magnification. Papers are either teased 



