Hormell — Dielectric Constant of Paraffins. 443 



determined from four different specimens of each column. 

 The total pressure to which the paraffin was subjected when in 

 the mould was 2140 lbs., or 7 lbs. per sq. in. Moulding the 

 columns under pressure was the only way in which masses of 

 this size could be secured of anything like uniform density. 

 The dielectric constant of a column moulded without pressure 

 differed as much as 3 per cent from that of a column of the 

 same kind of paraffin moulded under pressure. 



In Table YI will be found the dielectric constant of two kinds 

 of oil, a paraffin oil and a " transformer oil." This grade of 

 paraffin oil is sometimes used for transformers, but the so-called 

 " transformer oil " is said by the wholesale dealers to be the 

 best oil procurable for transformer work. In order to make 

 the necessary measurements with these oils a telescoping box 

 was made and lined with tinfoil. The ends were constructed 

 of thin rubber plates and through them the Lecher wires were 

 stretched. When the nodes rested on or near the rubber ends 

 the wave length in air was not changed by the presence of the 

 box. The box was filled with oil and the length adjusted 

 until the outer end rested on the third node. The box was 

 also filled with melted paraffin and the temperature effect on 

 the position of the node was noted. 



Table V shows how the index of refraction and therefore 

 the dielectric constant increased as the temperature decreased. 

 It is very probable that the change of the dielectric constant 

 can be accounted for on the ground of the change in density. 

 The densities at 79° C. and at 18° C. are given in the table. 



Table V. 



Index of Dielectric 



Temperature. refraction. constant. Density. 



79° C. 1-44(7) 2-09(5) '764 



71 C. 1-45(6) 2-12(5) 



65 C. 1-46(3) 2-14(0) 



56-5 C. 1*47(1) 2-16(3) 



53-7 C. 1-47(5) 2-17(6) 



18 C. 1-48(2) 2-19(8) -908 



In order to illustrate the method by which the dielectric 

 constant of each column for each wave length was determined, 

 I have selected a set of readings at random. They are the 

 data secured for column I of the number 120 paraffin. 



Diameter of primary 5 -00 cm 



Length of wave in air _ 40*85 



Length of tube wave 39*24 



Length of column . _ 83 -00 



