1894.] MICROSCOPICAL JOURNAL. 85 



coats of gold-size are then, in the same way, put on it. 

 I do not think that more coatings of gold-size are neces- 

 sary and the cell can be finished with a coating of a fancy 

 cement if it is wished. Blue, red, white, yellow or black 

 will do. But with slides for my own cabinet, I prefer 

 gold-size alone. This is all, and the object will keep 

 generally for years. When exposed to wide variations 

 of temperature, as are common in this climate, no cement 

 is always trusty. A majority of slides keep well but a 

 minority spoil by leaking. I say the preservative must 

 be watery, for strong alcohol or, what is worse, bisul- 

 phide of carbon or turpentine will dissolve the wall of 

 the cell and the slide will inevitably leak sooner or 

 later. 



Now I come to the use of other cements than gold-size 

 for microscopic purposes, and first, aspbaltum. Asphal- 

 tum dissolved in turpentine is used as a dryer by the 

 painters, but asphaltum varnish contains more asphaltum 

 than this. Trinidad asphaltum is about the only asphal- 

 tum in commerce, I believe. But it is cheap, and it makes 

 a good durable cell. But it dissolves in weak alcohol 

 and in some other preservatives and therefore cannot be 

 used. 



White zinc made up with drying oil, or white paint 

 makes a pretty good cell; and red, vermillion, venitian 

 red, and ochre, yellow ochre paints make pretty good 

 cells also. But when gold-size is added to the paint, an 

 excellent cell varnish results. 



What I have found makes excellent varnishes both for 

 cells and finishing are the different cv)lored Star Enamels. 

 They are fine in texture, dry quickly and evidently con- 

 tain a varnish for they make a bright surface. I use 

 them for cells constantly. White for cells and oak color 

 or mahogany color for finishing. Bright red, green, blue, 

 yellow, or black make excellent varnishes for microscopic 

 use. 



