62 ELECTRICITY IN AGRICULTURE 
Il. 
The Electric Influence Machine and its Installation—As 
the old machines of Holtz and Wimshurst have shown, 
especially on prolonged use, many inconveniences, I have con- 
structed the type represented in Fig. 5 (facing p. 21), in which 
these inconveniences are, for the most part, removed. This 
machine consists of two cylinders of glass or ebonite, E, 
rotating in opposite directions, one within the other, 
and provided with metallic (tin) boats fixed on strips of 
tinfoil. Over the machine is placed a cover fitted with 
a drying apparatus not shown in the figure. The glass 
cylinders are covered with a special varnish to protect them 
from humidity, and the brushes are made of silver-thread, 
The machine is best charged if first put in rotation by 
some turns in the wrong direction, the outer cylinder going 
from the brushes of the transverse conductor against the 
points of the collector, and afterwards in the right direc- 
tion—that is to say, the outer cylinder rotating from the 
collector against the brushes, causing sparks to go between 
the separate spheres of the discharger. The spheres must 
be separated at least 2cm., and some sparks taken before 
the machine comes to full charge. In experiments on 
the land the machine must be installed in a dry room, 
preferably on an upper floor, but always some height over 
the soil. In this room the temperature must be kept 
always some degrees higher than the outside. In such 
places the drying apparatus referred to above is not neces- 
sary, but the cover must always be kept over the machine 
to protect it from dust. 
The machine charging the positive pole must be con- 
nected to the insulated wire net by means of insulated 
copper wire, and the negative pole with a plate of zinc 
(o'5m2.) in humid soil. 
The method of distinguishing the negative from the 
positive pole is simple. Take away the connection of the 
Leyden jars with the poles on the one side and also the 
