Читать книгу Roentgen Rays and Phenomena of the Anode and Cathode онлайн

22 страница из 42

15. Gordon’s Experiment. Dust Particles Hasten Discharge. Gordon, Vol. II. Other experimenters had investigated the phenomena of the electric spark with different densities of the dielectric by a spark produced by a frictional or an influence machine, or, in a few cases, by powerful batteries without coils, while Gordon claims to be the first to carry out these experiments with an induction coil. He observed that when the discharging limit was nearly reached, small circumstances, such as a grain of dust or a rusting of the terminal by a former discharge, would cause the discharge to take place at a lower E. M. F., which should be allowed for.

16. Kelvin’s Experiment. Proc. R. So., 1860. Encyclo. Brit., Art. Elect. He used as the terminals, two plates. One of them was perfectly plane, while the other had a curvature of a very long radius. The object of this arrangement was to obtain a definite length of spark for each discharge. The plates were gradually moved away until the spark would no longer pass, and the reading of the distance was noted. The law which he found cannot well be expressed in the form of a rule or principle, because it is of a rather intricate nature, but a discovery resulted, namely in the case where the distance was greater, the dielectric strength was smaller for respective distances of .00254 and .535 cm. Many theoretical considerations in reference to this matter have been presented, notably that of Maxwell in his treatise on Electricity and Magnetism, Vol. I.