442 Hormell — Dielectric Constant of Paraffi 



ns. 



surface. Putting the argon tube and the movable bridge be- 

 yond the column of paraffin, and locating the first external 

 node (the fourth from the first bridge), it will be found that a 

 node (the third) will rest in the column 6 or 8 cm from the end. 

 Saw off a 2 cm slab from the end of the column and again locate 

 the node. Continue this until the wire node of the half tube 

 wave rests upon the end of the column. Frequent experi- 

 ments have shown that if the column be as much as l*5 cm too 

 long or too short, the position of the fourth node is not 

 affected. The conclusion, therefore, is that no error will be 

 made if the column of paraffin be l*5 cm too long or too short, 

 or the end be not against the first bridge. This fact makes it 

 very convenient when using the same column for different 

 wave lengths. 



This same column of proper length may be used to answer 

 the second question. After the position of the fourth node 

 has been determined, the column may be removed, and by 

 means of the table saw the section reduced to one 6 X 8 cm . The 

 process of locating the node and reducing the section may be 

 continued until the column is too thin to allow further reduc- 

 tion. 







Table IY. 









Area of 





Change in 



Effect on 



Size of 



cross 



Position of 



position 



one-half 



column. 



section. 



node. 



of node. 



wave length, 



V X 8 cm 



56 sq. cm 



120'34 cm 







6X8 



48 



120-20 







5X7 



35 



120-35 







4X6 



24 



120-28 







3X5 



15 



120*83 



. 5 cm 



, 2 cm 



2X4 



8 



123-60 



3-2 



l'l 



•5X35 



5-2 



126-68 



6-4 



2-3 



1X3 



3 



131-14 



11-8 



4-4 



Table IY shows the result of this experiment. From it we 

 learn that the effective field, so far as it can be determined by 

 means of an argon tube, certainly lies within a column whose 

 cross section is 5xT cm . By a comparison of the values in the 

 fifth column with those in the first, we find that the effect on 

 the half wave varies approximately inversely as the square of 

 the distance of the wires from the outer surface. 



Four specimens of the paraffin were secured from a wholesale 

 dealer. Thy were known as numbers 120, 125, 130 and 135, 

 their numbers representing their melting point on the Fahren- 

 heit scale. Two columns of each kind were prepared and the 

 melting point on the centigrade scale noted. The density was 



