290 E. W. Blake, Jr., on a method of producing 
are disposed four insulating posts, 
upon which the prepared. plate 1s 
aid. 
D is then made vertical, and is adjusted to the desired eke. | 
distance. An insulated connection being made between D an 
contact with the plate, and E depressed to the proper striking 
distance. The discharge having taken place, D is again made 
horizontal, and the plate fay be 
is process consists in gradually warming the plate over A 
ent. ; 
be overheated the figure is destroyed. It may be instantly 0; 
literated by exposure for a second to the naked flame, 20 
the plate may then be used again. The proper temperature oe 
scape al is some degrees below the real fusing poimt ° 
e us 
e figur 
and elevations of the excited surface. The depressions W d 
appear to be the true figures, as they correspond exactly m ie 
to those obtained by Lichtenberg. The plate may be duste 
before development ; the form thus revealed will be reproduced 12 
e : ‘is very difficult to measure, 0 to the elevations produc’ 
In films of 0-015 in. thickness, the deepest ines are about 0°005 
par. 
