414 
Proceedings of the Koyal Society of Edinburgh. [Sess. 
XXIV. — Experiment with the Spark Gap of an Induction Coil. 
By Dr Dawson Turner. 
If the electrodes of an induction coil be placed at such a distance that a 
spark will not pass easily, then the introduction of a dielectric between the 
poles will greatly facilitate the sparking, provided the dielectric be placed 
near or against the positive pole, but will not have this effect if placed 
against the negative pole. Experiments were made with mica, sulphur, 
glass, and ebonite, etc. 
( Issued separately July 8 , 1909 .) 
