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lilll.l. SYSTEM TECHNICAL JOURNAL 



sections arc cut, tliey must be further prepared by being stained, 

 dehydrated and cleared after which they are finally mounted in 

 Canada Balsam or similar mounting medium between a glass micro- 

 scope slide and a cover glass. Mounts of this kind are permanent, 

 but when it is not desired to retain the mounted specimen for record 

 or future examination, temporary mounts are often made in which 

 llu' iiiouiitint; iiudiuni is some liquid such as water or glycerine, or 



l-"ij!. It l'.(|iii|mu-nt I'cir tin- preparation ami proliniiMary examination of opatpK- 

 spriinuMis. 



in some cases, may be the staining medium itsell. An enl.u-ged \icw 

 of a permanenth' moimted trans\ersc radial and t.mgenti.d sections 

 of Douglas Fir wood is illustrated in Fig. IH. 



The iireparation of metallurgical siiecimens is ai (■nm|)lishc(! iiy 

 (lifTerent methods and if a six'cimen is to be exann'ned at extremely 

 hi^;h powers, the utmost in skill and refinement of methods is ncces- 

 s;ir\-. The usual method of jirocetlure is first to file a flat surface 

 on the specimen, after which the surface is gradually brought to a 

 semi-polished cf)ndition by rubbing the specimen on a sheet of French 

 emery paper, placed on a plane surface. A coarse grade of paper 

 is first emplo\ed and by gradual steps, finer and finer grade papers 

 are used, the rubbing on each successive paper being in a direction 

 at right angles to the preceding paper and continued until the scratches 



