132 Charles E. Benham — Liquid Inclusions in Glass. 



resin envelops thousands of aqueous globules and permanently shuts 

 in these inclusions so that a fragment of such impregnated resin, 

 if afterwards softened by heat and gently pressed between a glass 

 slip and cover-glass, makes a beautiful microscopic object, showing 

 myriads of liquid spherules each containing (when the gamboge is 

 used) a glittering galaxy of ever-moving particles as seen with 

 dark-ground illumination. 



Pig. 1. — Salt crystal with microscopic cavities containing brine and an 

 air bubble, the smallest of which show Brownian movement. 



Many of these spherical inclusions, moreover, are not entirely 

 filled with liquid, but show a central air bubble with a diameter about 

 one-third of that of the sphere. Around this is seen a ring of the 

 suspended gamboge particles in rapid movement. The bubbles 

 themselves are generally much too large to show Brownian move- 

 ment. To ensure their presence the impregnated resin mass should 

 be left a few weeks after the boiling. 



The general effect is shown in Fig. 2, which exhibits the various 

 sizes of the spherules, some filled completely with liquid and gamboge 

 particles, others having a central air globule. 



An experiment made with a view to imitate much more closely 

 in glass, by artificial means, the liquid inclusions of certain minerals 

 may be worth describing. 



r, A small glass tube, containing water and hermetically sealed, 

 (Was enclosed in the interior of an unbaked brick, and then submitted 

 ,(by the kindness of Messrs. H. Everett & Son, of Colchester) to the 



