Ncm Forms of Stereometers. 



305 



Fig. 4. 



Another form of stereometer (Fig. 5) somewhat re- 

 sembling that of Miller, was described in 1845 by Regnault 

 (Annates de Chirnie et de Physique (3), XIV, 207). 



In this instrument either decrease or increase of pressure 

 <:an be employed, and the apparatus is so arranged that it 

 can be filled with dry air. Notice is also made here of the 

 fact that some porous substances absorb air. This is detected 

 by the fact that they give different results according as the 

 pressure is increased or diminished. 



