MOUNTING AND PREPARATION OF OBJECTS. 55 



paration, the specimen is placed on a square of thin 

 glass, (which may be fastened to an ordinary wooden 

 slip or not, preferably not), and covered after the 

 application of a suitable medium with another 

 square of the same size, both if not fastened by the 

 medium itself are cemented by passing a brush 

 charged with any of the usual varnishes round their 

 edges. When dry they are either permanently in- 

 serted in a boxwood slip A, fig. 23, or what is much 

 more convenient, placed when required for examina- 

 tion within or on one, by any of the methods shown 

 in the figure. 



The advantages claimed for this plan are, con- 

 venience of storage, postal transmission, etc. ; possi- 

 bility of examining both sides of the specimen ; a 

 high power objective sustains no injury if it happens 

 to be driven through the preparation ; the aberra- 

 tions caused by the thickness of the glass slides 

 usually employed, are removed ; and when using high 

 powers the condenser can be brought close to the 

 object. The examination of objects with oblique 

 light is facilitated, their definition wonderfully im- 

 proved ; and even with direct light markings can be 

 seen, which defy resolution if the object be mounted 

 in the usual way ; finally one slip alone is necessary 

 for the reception of any preparation requiring ex- 

 amination. 



Many objects, among which may be mentioned, 

 scales of moths and butterflies, etc., require no 

 previous preparation, all that is necessary after 

 placing them between thin glass, is to pass a 



