TROWBRIDGE. — POSITIVE RAYS. 



517 



that the band 



proving again tliat the band (Figure 5) was made up of positive 

 rays. A large storage battery proved the best means of studying 

 the positive band, for the phenomenon was 

 not confused by the make and break of 

 mechanical or electrolytic interrupters. It 

 was soon discovered that a narrow phospho- 

 rescent band was formed on the side of the 

 septum which shielded the end of the tube. 

 The explanation of the band in the tube 

 without the septum was evidently this : the 

 pilot spark produces a number of positive 

 rays of different velocities which spread out 

 in the form of a cone, of which the apex is 

 the narrow orifice in the cathode terminal. 

 Under the influence of the magnetic field 

 these rays whirl around in the field somewhat 

 in the manner indicated by the dotted lines (Figure G). 



1'lGURE 6. 



In the expression p = 



ev 



p can have many values, depending 



mil sin i 



upon the values of r'. The narrowness of the band results from the 

 electrodynamic attraction of the whirls in a manner similar to the at- 

 traction of electrical currents all moving in the same direction. The 

 band may be called a magnetic spectrum, since it is produced by many 

 rays of different velocities. 



W. Wien 2 has shown that positive rays emanate from the anode, and 

 that these rays can be diverted by an ordinary horseshoe magnet. 

 The rays which I have investigated are undoubtedly of the same na- 

 ture as those studied by Wien. Their connection, however, with the 

 pilot discharge from a condenser is an added point of interest. 



Jefferson Physical Laboratory, 

 Harvard University. 



2 Wien, Ann., 65, 449-450 (1898). 



