The Microscope. 123 



WAYS • ^m 



AND/AEANS- 



Polarizing with a single nicol. — I made a discover}- the 

 other day which after all may be an old thing. I can polarize 

 with only one Nicol (as analyzer), the conditio sine qua being a 

 blue sky, especially the day after a rain. For greater conven- 

 ience I have extemporized a holder for the analyzer which I slip 



■ over the eye-piece. Starch " crosses " very distinctly, but of 

 course fainter than in regular polarization. For color, I put the 

 selenite on top of the slide ; the colors are also somewhat fainter. 

 The selenite is effective anywhere, so it be placed beneath the 

 analyzer. This comes handy in two ways : 1. It is possible to 

 get polarizing effects with a stand not provided with a substage. 

 2. When in the course of examination we want to see whether 

 the object will polarize, the Nicol slipped over the eye-piece will 

 quickly tell us whether it is worth while to apply the polarizer 

 in the regular way. But with any other sky than a blue one, 

 the trial will be a failure. With ordinary lamp light I succeeded 

 in getting faint indications, due of course to the position of the 



.mirror. — hans m. wilder. 



A RE-AGENT BOTTLE. 

 e. b. knerr. 



A veiy inexpensive yet very serviceable re-agent bottle may 

 loe made as follows : 



To an ordinary ounce or half ounce bottle with wide mouth, 

 a suitable cork of wood or rubber is fitted. Through the cork 

 is passed a piece of glass tubing I inch in diameter and of suf- 

 ficient length to reach near the bottom of the bottle and yet 

 extend ^ to ^ inch above the cork. Over this \ inch slip a piece 

 of I inch rubber tubing about H inches long, and close the upper 

 end by inserting about r,? inch of the core that was removed 

 from the cork by the cork-borer. The lower end of the glass 

 tube should be drawn out to a narrow opening. The glass tubes 

 may be made by softening a piece of tubing over a spirit lamp 

 or gas flame and drawing out. It is convenient to make a num- 



