440 .4. W. Wright— Forms of the Electrical Dischmy iu i 



distinct, and more higlily luminous, and %vlien tht- ■ 

 between the poles is so small that the branches are se|);.r; • 

 a comparatively small intei-val, we may have the weal< ~ 

 Finally, when the quantity of the electricity is increased, 

 tension at the poles becomes greater, or the distance 1- 

 them is lessened, the branches of the primary dischaiv 

 become so much extended as to meet, or at least to coin' 

 close proximity. Now it is well known that when a bo i 

 been traversed by or charged w4th electricity either posit- 

 negative, it becomes a better conductor for electricity ■ 

 opposite nature. In case then any branch from one si li 

 the positive, should meet one from the other side, nam. ! 

 negative, each would form for the electricity of the . >: 

 better path than the surrounding air, both from this can- 

 from the fact that it has a higher temperature. The maii 

 of the charge then would follow the path thus opened, ai 

 thread of air which it traverses being thereby very highly ! 

 would exhibit the intense brightness of the ordinary - 

 The fact that the discharge passes along the irregular br: 

 of the brush then sufficiently explains the crinkled and v;!; 

 ly contorted forms of the bright spark, when the teiisioa > 

 very great. With a machine affording electricity of high ten- 

 sion, the branches accompanying the bright sparks, when the 

 latter have a length of some inches, may be readily seen even 

 in the daylight. The longer and more numerous proceed from 

 toward the positive side, but those directed from the negative 

 are frequently visible. They are much shorter and less distmet 

 than the former. Sometinies short and faint branches issue 

 from different points of the negative pole itself, several r 

 •nee, simultaneous' 

 L the fact that the i 

 a better conductor by the intense keat, it migtt be ex] 

 that where a rapid succession of discharges passes, the si; 

 sive sparks would follow the same path, and therefore have :.• 

 same form, as the air- thread would not instantly communie;;t. 

 its heat to the air surrounding it. The researches of Fedder- 

 sen and of Prof Eood have shown that in the discharge of the 

 Leyden jar through a short interval, the spark is intermittent in 

 its character, consisting in fact of several discharges in rapu 

 succession. As the bright path appears to the eye single ami 

 sharply defined, it is very probable that their paths are a^i 

 identical, namely that of the first act of the discharge >» i^" 

 the Holtz machine also, used without condensers, the discharge^ 

 may be made so rapid when the poles are but an inch or les^ 

 apart, as to appear continiious, and to give a tone whose pijc ^ 

 can be definitely recognized. In such a case the lines oi Jiit 

 discharge seem to oscillate rapidly in a plane which has ditter- 



