8 THE MICROSCOPE. Jan. 



The time of exposure in bright sunlight will vary from 

 a minute or two (for transparent wings), to fifteen or 

 twenty minutes (for foliage leaves) — depending, of course, 

 on the degree of transparency or translucency of the 

 object. The print can be inspected from time to time 

 and the proper density of the picture secured. 



After exposure the prints can be fixed in a solution of 

 hyposulphite of soda. Or if handsome photographs are 

 desired, they can be toned in the gold solution commonly 

 used by photographers, and fixed in the usual manner. 



The process is so simple, so comparatively inexpensive, 

 and the results obtainable so interesting that it is believed 

 that the reward will be fully commensurate with the 

 time and energy expended. 



Moisture on the Cover Glass. — The cause of a deposit of 

 moisture on the under side of the cover-glass must be sealing 

 up before the object or the base on which it lies is thoroughly 

 dry, or perhaps through the ring not being cemented properly 

 on the glass slip, and so allowing the medium in which the fin- 

 ishing cement is dissolved to get through into the cavity in the 

 cell in which the object lies, and condensing on the cover. The 

 cure: With a sharp knife scrape off the ring of cement which 

 lies on the surface of the cover- glass, also slightly down the 

 side, about the thickness of the same; then warm the cover- 

 glass slightly over a small spirit lamp, moving it about to pre- 

 vent cracking it, and it should be then easily removable with 

 the knife without injury either to the glass or object ; then, before 

 replacing, take care that the object is thoroughly dry. If the 

 ring springs off instead of the cover-glass only, dry thoroughly ; 

 then put just sufficient cement on the underside of it to attach 

 it to the glass, and let this dry thoroughly before finishing off. 



Slides for Sale. — The Jersey Biological Station (England)- 

 will issue a quarterly publication and a series of 14 microscop- 

 ical preparations of the rare and the less renown marine organ- 

 isms. The text will describe the slides and give notes upon ma- 

 nipulation. The price is $5.2e5 for the year. Only 75 copies 

 will be issued. 



