22S 



Mechanical Disintegration caused by Positive Ions. 



sand-blast action of the ions. This region, when examined 

 with a low-power microscope, revealed the presence of a 

 series of short little grooves cut into the glass, all converging 

 m a direction parallel to the axis of the tube and presenting 

 a pretty pattern, as illustrated in fig. 3 (a). 



Fig". 3. 



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(«) (&) 



On examining the similar streak diametrically opposite, 

 caused by the impact of ions from the reverse current it 

 was interesting to note that they all gave a pattern of grooves 

 quite similar, as shown in fig. 3 (6), but with the grooves 

 converging in a direction exactly opposite. 



There can be very little doubt that this grooving of the 

 glass was effected by the bombardment of the massive positive 

 ions which travel in opposite directions in the two streams 

 causing grooves that converge in opposite directions. A 

 closer examination, taking into consideration the direction of 

 the currents and the deflecting field, confirmed the truth of 

 the above explanation. To make the point sure, with a point 

 and plate in series with the tube the reverse current was 

 practically cutoff, and the corresponding streak disappeared 

 accordingly. When the upper electrode was the cathode, 

 and the lines of force passed from left to right, the grooving 

 was found to be on the side away from the observer and 

 converging upwards, as would be the case if the positive ions- 

 were the cause of this peculiar corrosion. 



Fig. 4 is an enlarged view through the capillary of a dis- 

 charge-tube in which the grooves have been formed, taken 



