264 Prof. Riess on Electric Pauses. 



witliiu 1 or 2 lines of tlie sphere, tlie streaming out is very vio- 

 lent, and the remaining density of the sphere only sufficient for 

 sparks of the same length. If the point be withdrawn to a 

 greater distance from the sphere, the streaming out diminishes, 

 but not to an extent sufficient to leave the sphere a density ne- 

 cessary for sparks of more than 2 lines in length. The sparks 

 do not appear, and the same is true of all larger distances. If 

 the point be withdrawn so far that all streaming out ceases, the 

 distance must be much greater than 4 inches, and then the un- 

 enfeebled density of the sphere is insufficient for sparks of such a 

 length. This process also takes place when the form of the body 

 brought near the sphere is difiPerent : sparks are obtained up to 

 a certain length, and none beyond this. Only by a definite rela- 

 tion of the action of the machine to the magnitude of an ap- 

 proximated sphere can the pause phsenomenon occur between two 

 spheres, as observed in the experiment of Nairne. Such an ex- 

 periment is not to be repeated with certainty. But the effect is 

 certain, because independent to a greater extent of the action of 

 the machine, when the truncated cone (the pause-cone) is made 

 use of. At the closest approximation of the cone to the sphere, 

 the augmentation of the density, and the consequent streaming 

 out of the electricity, is not sufficient to hinder the production 

 of sparks. On the diminution of this density with increasing 

 distance, the sparks could never disappear if the disappearance 

 were not effected by the increased number of the emissive points, 

 or in other words, by the breadth of the luminous segment of 

 the sphere. At the shortest distance at which the sparks are 

 absent (9 lines) this breadth is not considerable, but it augments 

 with the increasing distance until the density throughout the 

 extent of the segment has sunk below the limit necessary for the 

 streaming out of the electricity. From this point forward the width 

 of the segment diminishes. At the distance of 1^ inch, where 

 the luminous segment is about i an inch wide, the density upon 

 it had sunk so far that the tranquil glow was no longer seen 

 alone, but from the edge of the segment single luminous fibres 

 issued in the form of a brush. At a greater distance, therefore, 

 the sparks appeared again, and continued so long as the con- 

 ductor yielded sparks. If the form of the cone be altered only 

 a little by rendering the frustum shorter, sparks are obtained 

 at all the distances mentioned ; if it be made a little sharper, 

 sparks are obtained up to a certain point, and none afterwards. 

 In like manner no pauses were obtained with larger and 

 smaller spheres than those for which the cone has been arranged. 

 We convince ourselves easily of the change in the arrangement 

 of the electricity on the cone, and the extinction of the pauses 

 thereby produced, if during the experiment a conducting body 



