40 THE MICROSCOPE 



of oil of turpentine. The best black is made by boiling together 

 a quarter of a pound of foreign asphaltum and 4^ ozs. of linseed 

 oil, which has been previously boiled with h oz. of litharge until 

 quite stringy. The mass is then mixed with half a pint of oil of 

 turpentine, or as much as may be required to make it of a proper 

 consistency. It is often improved by being thickened with lamp- 

 black. Dr. Euienstein, of Stuttgart, finds that equal parts of 

 Brunswick black and gold-size, with a very little Canada balsam, 

 form a very lasting cement. I find a good substitute for Bruns- 

 wick black in the "liquid stove-polish." 



Electrical Cement— Melt together five parts of resin, one of 

 bees'-wax, and one of red ochre. It must be used whilst hot, and 

 can be readily moulded into any form. It is often employed in 

 making shallow cells for liquid mounts. 



Mask-Lac. — This is a very good quick-drying cement, espe- 

 cially for wet preparations, and also as a coating for specimens 

 mounted in Canada balsam or copal. The variety of lac is 

 designated as No. 3 at Beseler's lac factory in Berlin (Schiitzen 

 Strasse, No. 66). 



Shellac and Aniline (Thiersch). — After the specimens have been 

 mounted in Canada balsam, surround with a border of Canada bal- 

 sam dissolved in chloroform. After the third or fourth day apply a 

 final coating, consisting of a thick varnish of shellac, coloured with a 

 filtered, concentrated solution of aniline blue or gamboge in abso- 

 lute alcohol. Finally, about a scruple of castor-oil is to be added 

 to each ounce of the mixture, and after some further evaporation 

 is to be preserved in a well-closed vessel. If after a time it 

 becomes too concentrated, a few drops of absolute alcohol may 

 be added. The varnish is to be applied to the border of the 

 balsam with a brush. It soon becomes hard and forms an elegant 

 and hermetic covering and finishing cement. 



Dr. Bastian's Cement. — This is much used in Germany, and is 

 the best cement for liquid cells. It is made by adding a consider- 

 able quantity of nitrate of bismuth to a solution of gum-mastic in 

 chloroform. It may be procured at almost any optician's. 



An Extra-Adhesive Gum. — Dissolve 2 drachms of isinglass in 

 4 oz. of distilled vinegar; add as much gum arable as will give it 

 the required consistency. This keeps well, but is apt to become 



