194 Trowbridge — Magnetic Field and Coronal Streamers. 



negative ions, apparently, did not reach the anticathode, but 



instead formed fluorescent rings around the cathode. The 

 cathode is thus made part of a hollow hemisphere of, in 

 this case, orange light ; when, however, the bulb was excited 

 by a coil giving a twenty-inch spark with Leyden jars the 

 bulb gave very brilliant X-rays at the moment of exciting 



the magnetic field ; in the case of the use of the six-inch 

 spark coil, there were no Leyden jars in the circuit. 



Besides the scientific side of the manifestations of the 

 effect of the magnetic field on discharges in high vacua, 

 there seems to be a practical use of the electromagnetic field 

 in connection with the regulation of the discharge in X-ray 

 bulbs. At present, when the vacuum has risen so high that 

 the bulb cannot be excited, one is forced to apply heat to 

 various regulators in order to drive out gases to increase 

 the conduction. All regulators hitherto used are uncertain 

 and dangerous to the life of the bulb in their application. 

 I believe that a magnetic regulator applied to the anode would 

 be of great service in hospital plants where a suitable elec- 

 trical equipment can be had. The magnetic regulator is 

 entirely safe and is constant in its action. It also enables 

 one to pass readily from the production of hard rays to that 

 of soft rays by the modification of the strength of the 

 magnetic field ; a modification difficult to accomplish without 

 the application of the magnetic field. 



