7-t Scientific Intelligence. 



different strength, for various capacities of the Leyden jar and 

 for different forms of electrodes. 



It was found that as the length of the spark increases, the 

 total duration diminishes, which is also the case with the number 

 of partial sparks composing it, but the interval of time between 

 the partial sparks increases. For long sparks the mean interval 

 of time u between the partial sparks, was proportional to the 

 square root of the spark length, -\/l. For short sparks, u appears 

 to be greater than this law would demand ; also the time-intervals 

 between the two first partial discharges increase, as it appears, a 

 little more rapidly than \/l. When the length of the spark was 

 made less than 0'75 mm sparks were produced even on completing 

 the primary circuit, but in this case the number of the partial 

 discharges was much smaller and their mean distance apart 

 greater, than when the circuit was broken. 



When the strength of the primary current was diminished the 

 number of the partial discharges and the total duration were 

 quickly curtailed, but the mean time-interval of the partial dis- 

 charges stood in an inverse ratio to the current's strength. This 

 applies also to the value of the first time-interval. 



As the capacity of the Leyden jar was increased the discharge 

 consisted of a series of partial sparks with increasing time-inter- 

 vals. When the capacity was diminished the number of the 

 partial sparks increased and the discharge finally appeared partly 

 continuous. Since this continuous light did not sufficiently affect 

 the sensitive paper, the author made direct observations with a 

 revolving mirror, and ascertained that the aureole was preceded 

 by a few and followed by a greater number of partial sparks. 

 As the capacity was made smaller, the number of these sparks 

 was diminished, till finally the am-eole formed the greatest part 

 of the discharge. As long as the discharge was entirely disrup- 

 tive, a diminution of the capacity diminished the time-interval 

 between the partial sparks, but increased the total duration. For 

 short sparks, however, the total duration appears to approach a 

 constant quantity and to be independent of the capacity ; it is 

 about 0-023 sec. 



As the electrodes were made more pointed the entire duration 

 increased, also the number of the partial sparks, but the mean 

 time-interval between them was diminished. When the electrodes 

 were made very sharp, completion of the primary current pro- 

 duced sparks, but their number was small. All the experiments 

 show that the time-interval between the partial sparks increases 

 toward the end of the discharge, the last interval often being twice 

 as great as its predecessor. The author has expressed the rela- 

 tion of the time-intervals, reckoning from the first partial spark, 

 by an exponential function, and the agreement ■ between calcula- 

 tion and observation is very good if the last three time-intervals 

 are neglected. 



The results in their main features agree very well with the 

 observations of Rood, but differ from the others to a degree that 



