. The science-history of the universe . pa-rated the metallic coatings and the jar, and examining eachone for electrification, he found the metallic coatings prac-tically unelectrified, while the glass jar proved to be highlyelectrified. Upon replacing the coatings in the jar, hewas able to obtain a bright spark, just as tho the coatingshad not been removed. This experiment clearly provedthat the important part of such a Leyden jar or condenser ELECTROSTATICS 171 was the glass or dielectric and that the function of theconducting coatings was merely to spread the charge overthe glass. Taking su
. The science-history of the universe . pa-rated the metallic coatings and the jar, and examining eachone for electrification, he found the metallic coatings prac-tically unelectrified, while the glass jar proved to be highlyelectrified. Upon replacing the coatings in the jar, hewas able to obtain a bright spark, just as tho the coatingshad not been removed. This experiment clearly provedthat the important part of such a Leyden jar or condenser ELECTROSTATICS 171 was the glass or dielectric and that the function of theconducting coatings was merely to spread the charge overthe glass. Taking such a view, it will be readily seen thatthe larger the jar, the greater is the quantity of electricitywhich may be stored therein. Large jars are, however,often inconvenient to handle, so that a battery of suchjars is used having their inner coatings all connected to-gether to form one large coating, and the outer ones simi-larly connected. Fig. 10 shows such a battery, the outercoatings being connected by the tinfoil lining of the Experiment of Cuneus : the Leyden Jar. From time to time it has been attempted to use for thedielectric materials other than glass, and thousands ofcondensers using paraffined paper are in use on moderntelephone and telegraph circuits. Larger condensers areused on power circuits. None of these other materials is,however, as satisfactory as glass, being liable to be dis-rupted if the pressure of the charge is too great. The op-portunities for using condensers to advantage are rapidly 172 ELECTRICITY increasing at present and considerable energy is beingdirected toward their development. The desirable qualitiesof such a condenser are that its dielectric should be capableof containing a very large charge, that it should standvery high electric pressure without disruption, and that itscoatings should be in the most intimate contact with the
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