160 The Microscope. 



the rings shall be thoroughly dry — prepared at least forty- eight 

 hours, and preferably more, before using. I am now making 

 up my summer's supply of white zinc rings. It may be ob- 

 jected that so much drying consumes too much time. Slides 

 can be ringed at the rate of a gross an hour — and this at odd 

 moments when no other species of microscopical work is possi- 

 ble. These slides, packed in rack-boxes, occupy but little space, 

 are free from dust, and reliable slides are always ready for im- 

 mediate use. For striping, I use artists' colors ground in oil 

 and mixed in dammar. If a narrow, white zinc ring is desired, 

 a coat composed of copal varnish and Brown's rubber cement 

 preserves the oil-colors and gives firmness to the ring without 

 adding to its apparent width. 



In deep cells for opaque mounts, I do not find those slides 

 whose cells contain an aperture any more free from dewy de- 

 posits upon the cover than those which are hermetically sealed. 

 The following described cell I have found very satisfactory in 

 my own use. Use no volatile substance within the cell; paste 

 a dead black paper upon a white (not much glazed, and there- 

 fore absorbent) one, and from this cut with a gun-punch disks, 

 of the desired size ; center a slide and paste a disk upon it — 

 black side down, to exclude the light ; upon this cement with 

 gold-size a brass curtain-ring — flattened or not, according to the 

 depth of the cell required ; run on a background with any shade 

 of water-color paint which best exhibits the object, leaving a 

 white margin around the edge of the cell ; cement the cover 

 with a small quantity of white zinc to the ring ; color the cells 

 as may be desired ; run on the copal mixture already described, 

 giving added security to the cover and rounding out the cell. 

 This makes a neat and durable mount, and no dewy deposits 

 have ever, to my knowledge, appeared upon the covers of cells 

 so made. 



With regard to the prevention of " dewing " in transparent 

 mounts, I may add that I have found it essential that the objects 

 should be thoroughly dry. If diatoms, use the covers direct 

 from the brass mounting-table ; or if such have been breathed 

 upon, as scales, see that the moisture is fully evaporated, and 

 in sealing use the smallest quantity of cement consistent with 

 a perfect adhesion of the cover-glass. — Microscopical Bulletin, 



