Dr Turner's Analysis of Euchroite. 801 



ment or diminish the amplitude of its excursions, as Bichat 

 had supposed. He supposed, however contrary to the result 

 of experiment, that the tympanum unstretched itself for strong 

 impressions, and stretched itself to receive weak impressions. 



3. That the vibrations of that membrane communicate them- 

 selves, without any alteration to the labyrinth, by means of 

 the small bones, in the same manner as the vibrations of the up- 

 per table of an instrument are communicated to the lower 

 table. 



4. That the small bones modify also the excursions of the 

 vibrating parts of the organs contained in the labyrinth. 



5. That the cavity of the tympanum (Caisse du Tambour) 

 serves probably to keep up near the apertures of the labyrinth, 

 and the internal face of the membrane of the tympanum, an 

 aerial medium, whose physical properties are constant. 



Art. XXII. — Analysis of Euchroite. By Edward Tur- 

 ner, M. D. F. R. S. E. &c. Lecturer on Chemistry, and 

 Fellow of the Royal College of Physicians, Edinburgh. 



A small fragment of the new mineral species, Euchroite,* 

 having been presented to me for analysis by Mr Haidinger, I 

 proceeded to a chemical investigation of it in the following 

 manner. 



When heated in a clean glass tube per se, its water of cry- 

 stallization was disengaged, and this occurred at a tempera- 

 ture far short of redness. If the heat is gradually applied, it 

 suffers no decrepitation whatever, retaining its form complete- 

 ly ; its brilliant colour, however, is afterwards found to have 

 changed to a dull green, and it crumbles into powder under 

 the gentlest pressure. It undergoes no farther change on 

 glass, its point of perfect fusion being above that of diffi- 

 cultly fusible glass. Urged by the blow-pipe on a piece 

 of clean platinum, without exposure to the reducing flame, 



• See Mr Haidingcr's Description of Euchroite, p. 133 of the pre- 

 ceding Number. 



