368 The Microscope. 



dental supplies. It is soft and without grit in its substance. 

 It is exceedingly useful not only for cleaning and protecting 

 cover glasses, but for wiping the lenses and the eye-pieces of 

 the microscope. 



Dr. r. L, James, in his " Microscopical Technology," suggests 

 a coyer glass holder made by placing around a cork or some 

 other circular object, a coil of brass or of copper bell-spring, 

 the ends of the wire being thrust into the cork to hold it firmly 

 in place, and the cork with its burden of spring is fastened to a 

 heavy base. The cleaned covers are inserted into the spring, as 

 Dr. James remarks, much as a pen holder is inserted into simi- 

 lar spring-racks. The whole is then protected from the dust, 

 and the covers remain clean and are conveniently reached when 

 wanted. 



MORE ABOUT CEMENTS.— II. 



J. D. BECK. 



BY mixing plenty of moist Chinese white with the colorless 

 cement, and grinding it thoroughly in a mortar and placing 

 it in a bottle with a sufficient quantitj^ of glycerine to prevent 

 cracking, you will have a beautiful and durable white cement. 

 On a fair trial it will be found that these cements will have no 

 equal for durability and tenacity on glass, and that they will 

 not run into balsam mounts if the latter are sufficiently hard for 

 any cement which dries quickly. 



It will be necessary to give the rings made of these cements 

 several coats of amber varnish or the best copal varnish, so as 

 to resist moisture. I do not recommend these colored cements 

 for aqueous mounts lest they run in. Balsam, gelatine or gum 

 mounts, when neatly finished with the following transparent 

 cements are unequaled in beauty, and probably as durable as 

 any; they never ruin any mounts by running in, and save the 

 time consumed in ornamenting, which really adds no essential 

 value to slides. Procure a good colorless amber, or best color- 

 less copal varnish, and add a little white beeswax to one bottle 

 of amber or of copal varnish or palmitate of alumina* instead of 

 wax, and it will increase the tenacity and elasticity of the cements 

 which are to be used for the body of the ring around moist or 



*Pissolve in oil of turpentine. 



