SCALE of 0 .02. inclx 
De La Rue & Midler. 
Phil. Trans. 1878 . Plate 8 . 
CURVES OF LEN GTH OF SPARK BETWEEN A POINT A DISC. 
10 
00 20 
00 30 
00 40 
00 50 
00 60 
t- 
o 
o 
00 80 
o 
o 
Warren De LaRue .deD Q‘ J Pound . Sculpt 
