Prof. Riess on Electric Pauses. 266 



is brought near the sphere, while a sphere is placed near the 

 prime conductor at a suitable place. Under the large sphere, A, 

 of the conductor (fig. 1) a small sphere was placed at a distance 

 of 9 lines, and the pause-cone removed to a distance of 1 inch 

 from the pause-sphere. By the most persistent turning of the 

 machine no spark appeared at either of the intervals. When, 

 however, the hand was approached from above to within a distance 

 of 10 inches, sparks passed incessantly to the lower sphere A; 

 and, when the hand was removed, again disappeared. In the 

 dark it was observed that by the approximation of the hand 

 the luminous segment was extinguished upon the pause-sphere. 

 Here, therefore, by the approximation of a conductor, the arrange- 

 ment on the sphere was changed, by this the streaming out of 

 the electricity prevented, and the quantity of electricity remain- 

 ing on the conductor augmented. The electricity of the pause- 

 sphere is not only diminished by the streaming out of the elec- 

 tricity, but also by the circumstance that the brush of the adja- 

 cent pause-cone sends air negatively electrified against it. This 

 circumstance cannot, however, cause the absence of the sparks, 

 which was at once shown when the conductor of the machine 

 was negatively electrified. Although the machine yielded nega- 

 tive electricity in a less quantity than positive, and although 

 here the pause-cone sent a much longer brush against the sphere, 

 still sparks varjang from | of an inch to 2 inches in length 

 were easily obtained ; which were absent when the conductor 

 was charged positively. The phsenomenon of the pauses was 

 not in this case perfectly exhibited, being characterized by the 

 fact that at some distances between the electrodes (1, ]^, 1|- 

 inch) the sparks passed tardily and irregularly, and were some- 

 times mixed with hissing brushes ; while, when a conductor was 

 brought near, the regularity of the process was established. As 

 there is no doubt that the arrangement of the negative electricity 

 on the sphei'C was precisely the same as that of the positive in 

 the former experiments, these irregularities in the pauses would 

 be very surprising, were we not aware of the fact, that in free air 

 negative electricity is brought with much more difficulty to the 

 state of glow than positive. Thus at the rounded end of a me- 

 tallic cylinder, 0*3 of an inch in thickness, Faraday easily ob- 

 tained the glow with positive electricity, but failed to obtain it 

 with negative electricity. (Experimental Researches, 530.) The 

 imperfection of the pauses with negative electricity, is due to the 

 difficulty of obtaining the glow with this kind of electricity, and 

 furnishes an additional proof that the pauses are determined by 

 the glowing of the sphere. 



In the explanation of the pauses just given, one difficulty 

 remains untouched, which appears to be of general interest, inas- 



