46*4 Dr. Carl Barus on the, Absorption of 



result is a light, very white pumice, larging exuding from 

 the capillary canal (as shown in fig. 1), the part remaining 

 within resembling pith. In this way the enlarged bore of 

 the tube may be clearly compared with the parts left free 



'8-8 mm. 



Omm. 



Fig. 1. — Capillar/ tube, with water-glass core heated above. 



Figs. 2-13. — Diagrams. The cross-hatched parts denote the core of 

 water-glass (much enlarged), the envelope of igneous glass being 

 ignored. Mercury is shown in black ; cavities in white ; residual 

 water (?) is differently cross-hatched. The actual contours were 

 usually more ovoid than these figures. 



from water and in contact with mercury only. On further 

 fusion the pumice melts igneously, and, if the glass contains 

 lead, it turns black in the usual way on reduction. 



