146 Dr. E. H. Barton on the Attenuation of Electric Waves 



a function of the attenuation constant and the dimensions of 

 the line, and would appear to be immediately calculable. But 

 this is not all. For the above is on the assumption that 

 the losses occur only along the wires themselves, whereas 

 something is lost also on reflexion at the primary oscillator 

 where the waves are generated. This fact soon became 

 apparent on the repetition of the experiment with different 

 lengths of line, and the value of this reflexion coefficient 

 was substantially confirmed by further experiments and by 

 the application of this new view of the case to experiments 

 previously carried out in Bonn. 



Experimental Arrangement. — The arrangement of the ap- 

 paratus adopted in the determination is diagrammatically 

 represented in fig. 1. In this figure, A denotes the battery 



Rk. 1. 



"^ I 



of two storage-cells, B and C are the primary and secondary 

 coils respectively of the induction-coil, of which C has a 

 resistance of 3000 ohms and an inductance of about 20 

 henries. G is the spark-gap, which was adjusted to 2 mm. 

 The wire PGP', measured along the semicircle, was about 

 2 m. PP' are condenser-plates of zinc 40 cm. diam. placed 

 opposite to and 30 cm. distant from the precisely similar 

 plates SS'. The line is represented by SB TT'E' S', and 

 consists of two parallel copper wires 1'5 mm. diam., and kept 

 8 cm. apart by wood separators at intervals of about 2 m. 

 E E' denotes the electrometer, which has a single plane 

 needle, initially uncharged, and suspended by a fine quartz 

 fibre between two disks attached to the line at E and E'. The 

 needle is therefore electrified by induction whenever a wave 

 passes E E', and its ends are consequently attracted to the 

 disks whatever the sign of their potential-difference. T T' 

 signifies the several pieces of apparatus successively used at 

 or near the end of the line, and will be described in detail for 

 each case when dealt with. The lengths of the line before 

 and after the electrometer will also be stated in connexion 

 with each experiment. The waves generated by the primary 

 oscillator were about 8*5 m. long. 



Theory. — Let 8 l be the electrometer-throw obtained when 

 a completely absorbing bridge is used at T T' (fig. 1), and let 



