605 



is the appearance of a direction of a force emanating from the 

 negative. 



In some of the vacuum-tubes beyond the clear cloud-like stratifica- 

 tions, but nearer the negative terminal, several faint striae can be 

 obtained : on repeating Mr. Grove's experiment (Phil. Mag. July 

 1858), of allowing the discharge to pass between two metallic points 

 attached to the coil, the author observed that these faint striae in- 

 variably disappeared. 



Stratifications remarkably sensitive to induction on the approach 

 of the hand were obtained in a glass cylinder of about 4-|- inches dia- 

 meter, in which the wires were hermetically sealed 21 inches apart. 



From the absorption of carbonic acid by caustic potassa, not only 

 were vacua obtained far more perfect than by the Torricellian method, 

 but the process can be made so gradual as to occupy several 

 weeks, or even months, thus enabling the experimenter to examine 

 the phenomena of the stratified discharge under a variety of con- 

 ditions, several of which the author describes ; in this manner the 

 non-transferring condition for the electrical discharge in a vacuum 

 has been experimentally ascertained. The author considers that 

 this confirms the opinion he ventured to offer in his previous 

 paper; for if the pulsations or vibrations of an electrical discharge are 

 greatest in the bright bands and least in the obscure, this system of 

 interference or of pulsations would also account for the entire absence 

 of stratifications when the air or gas is not sufficiently rarefied, as 

 well as when the vacuum becomes nearly perfect, while the gradual 

 change of narrow to cloud-like stratifications is thus satisfactorily 

 explained. 



In an additional note to his Paper, the author describes some 

 farther experiments, particularly one of moving the vacuum-tube to 

 and fro in a rapid manner, or rotating it in a plane, while the dis- 

 charges are made, either singly or continuously : in the latter case the 

 stratified discharges are separated, giving the appearance of an illumi- 

 nated fan or wheel ; in the former, only a single discharge is per- 

 ceptible, taking place in whatever direction the tube may at the 

 instant be placed. The author considers this experiment as con- 

 firmatory of his former opinion, that the stratifications are entirely 

 due to a single disruption of the primary circuit. 



The experiments, as described in the Paper, were exhibited by the 

 author to the Society. 



