24 THE MICROSCOPE. Feb., 



of balsam or balsam dissolved in benzole in the center of 

 the glass slide, take your object out of the turpentine it 

 is soaked in, with a small pair of pliers, and place it in 

 the balsam with the hollow curved side of the prepara- 

 tion down if it is not quite flat. Then turn it over on 

 the other side to release any air bubbles that may be en 

 closed underneath, then adjust it well in the center with 

 a needle point, put a drop of balsam on the top, and place 

 the slide on one side protected from the dust for 24 

 hours. 



Clean a cover-glass the size you wish to use, see that 

 the preparation is well centered. If it is not right it can 

 be moved by the needle point, the balsam not being hard 

 enough to prevent it, but if the preparation is very deli- 

 cate, it will be necessary to warm the slide on the hot- 

 table to soften the balsam before attempting to disturb 

 it ; when everything is right, place a drop of balsam on 

 the top. This is to fill up any hollow that may form in 

 the center of the balsam, which would hold the air when 

 the cover is put on it. Place the cover gently in the 

 middle of the slide, letting it sink down by its own 

 weight at first, press gently with the needle, being care- 

 fulto have the cover properly in the center. If not quite 

 centered, shift it with the needle point till it is quite 

 true. The pi'eparation will not move in the balsam for 

 some time till the fresh balsam has penetrated through 

 the dried balsam put on the day before. If you find that 

 the object has moved out of the center then comes the 

 difiiculty of getting it back again without beginning the 

 whole process over again. Have two needles by you, as 

 one is sure to get messed with balsam which will get on 

 the front of the cover- glass and bother you in centering 

 the object. Notice to which edge of the cover-glass the 

 object is nearest, and with the needle point draw the 

 cover-glass by pressing on the top towards the edge of 

 the slide. In this way the cover will slip over the 



