HISTORY AND PROGRESS. 207 



current, but was at the same time so thin that a spark of 

 static electricity of moderate tension could easily spring from 

 one plate to the other. From the corners of each of the 

 plates a conducting wire went to the apparatus below. 



The whole was fixed on the roof by an insulated support, 

 and, of course, protected by screens from rain and wind. 



In the event of the passage of atmospheric electricity of 

 high tension along the line on one side, for instance, it would 

 spring over from plate to plate, rather than traverse the fine 

 wire forming the coils of the apparatus, and would go on by 

 the other line to the next station ; Steinheil's intention being 

 to conduct the high tension electricity along the line, and to 

 allow the apparatus to escape. 



106. Meissner's Lightning Discharger. SteinheiPs dis- 

 charger had been constructed with the sole view of affording 

 the static electricity a short circuit across the apparatus 

 whilst the fluid passed in the same line circuit as the galvanic 

 current, from end to end. Meissner introduced the method 

 of conducting the electricity directly from the discharger to 

 earth a method much more in accordance with the nature 

 of the electricity itself. 



Fig. 113 gives a perspective view of Meissner's lightning 

 discharger. The upper plate, A, is of copper, 8 inches 

 long, 4 inches broad, and three^eighths of an inch thick ; 



Fig. 113. 



it is fastened to a second plate, B, of somewhat larger dimen- 

 sions, by means of screws, n n n n. The two plates are, 



