of Electricity through Gases. 191 



Table IV. — Values of R for Spark Potential between 

 . Spherical Surfaces in Electrostatic Units. 



Explosive 

 distance in 

 centimetres. 



Radius of Spheres in centimetres. 



1 



05 



025 



o-oi 



0-02 

 0-03 

 0-04 

 0-05 

 06 

 0-07 

 0-08 

 0-09 



o-io 



Oil 

 0-12 

 0-14 



336 

 258 

 224 

 206 

 194 

 184 

 175 

 172 

 165 

 164 

 160 

 159 

 154 



347 

 262 

 236 

 213 

 202 

 190 

 183 

 179 

 174 

 171 

 167 

 167 

 164 



372 



277 

 240 

 222 

 215 

 202 

 193 

 192 

 187 

 187 

 183 

 185 

 187 



010 

 0-15 

 0-20 

 025 

 0-30 

 0-35 

 040 

 0-45 

 0-50 

 0-55 

 0-60 

 0-70 

 0-80 

 090 

 1-00 

 1-20 

 1-50 



166 

 155 

 148 

 145 

 143 

 143 

 142 

 142 

 144 

 145 

 145 

 148 

 151 



175 



165 

 162 

 161 

 163 

 166 

 170 

 174 

 180 

 184 

 190 

 196 

 205 



190 

 190 



198 

 204 

 215 

 226 

 236 

 249 

 256 

 265 

 272 

 281 

 288 

 293 

 301 

 312 

 327 



In Table IV. Paschen's* recent observations have been 

 similarly reduced. I have taken the values which Paschen 

 gives for the potential necessary to produce the first spark, 

 which, according to him, are slightly larger than those for 

 the subsequent sparks. 



Tables III. and IV. will be found to agree with each other 

 in their main features ; and considering the many disturbing 

 influences to which such difficult measurements are subject. 

 the individual numbers also compare well with each other. 

 The main facts which, whatever their causes, can be deduced 

 from the Tables are as follows : — 



* Wiedemann's Amialen, xxxvii. p. 09 (1880). 



P2 



