Method of Determining Vapour-Densities. 405 



the balloon. The facility with which the balloon can be 

 sealed up is not among the least of the advantages of my mo- 

 dification. On softening Wyq glass at c by means of the blow- 

 pipe-flaniCj tlie capillary tube immediately collapses by the 

 pressure of the air ; and the fine glass threads formed by the 

 withdrawal of the bulb-tube can easily be melted before the 

 flame into a bead. The reading-ofF of the manometer needs 



no particular hurry, because its height is comparatively fixed 

 by the withdrawal of the bulb-tube. 



The height of the manometer having been read off, the air 

 Phil Mag, S. .5. A^ol. 4. No. 27. Dec, 1877. 2 H 



