30 AQUATIC MICROSCOPY FOR BEGINNERS. 



in better position, and the whole can be turned about, 

 if the pasteboard is fastened to a strip of wood, and a 

 small pin is driven into each corner. When the ring' 

 is made, put the slip in a warm place until the cement 

 is hard, or hold it over the lamp-flame for a few mo- 

 ments at a time, taking care not to allow the shellac 

 to boil, or the bubbles will never disappear and the 

 ring will be weakened. These lamp-dried rings are 

 hard as soon as cold, and they adhere so firmly that 

 they can only be scraped off with a knife and hard 

 work. They have the further advantage of being 

 rapidly made. 



A deeper and perhaps a somewhat neater cell can be 

 formed from paper. Cut a circular disk, of the di- 

 ameter of the ring required, from porous paper as thick 

 as the depth of the desired cell, and from the center 

 cut out a smaller disk, thus leaving a narrow ring. 

 Soak this ring in thin shellac cement until its pores are 

 filled with the liquid, and hang it on a pin in a warm 

 place to dry. Several can be prepared at once, and of 

 different size and thickness. They are to be fastened 

 to the slip by touching one side with a little shellac and 

 pressing the glass on it and allowing it to dry; or by 

 gently heating the slip and the ring together over the 

 lamp. It is well to prepare several slips at one time, 

 so as to have them ready for an emergency, as, for in- 

 stance, after an excellent gathering of microscopical 

 material has been made, and the student is so anxious 

 to see what he has that he cannot take time to clean 

 the slide and cover after a hasty glance for rarities, 

 but must have another ready at a moment's notice. 



To mount dry objects, permanently, such as pollen, 

 seeds, scales from insect-wings, and other things suita- 



