AND HORTICULTURE. 63 
conducting wire (to earth or the insulated wire net), and put 
the spheres of the discharger at a distance apart of about 
15 cm. Ifthe machine is moved a stream of light is seen 
between the spheres, violet on the side of the negative 
pole, with a small bright spot on the sphere, white and 
very bright, on the positive side. The machine is easily 
made to perform this experiment. As the machine, when 
stopped, very frequently changes its poles, this experi- 
ment must always be repeated and the machine continue 
in motion before fixing the conducting wires. 
The new machine does not give so long a spark as the 
older one, but the quantity of electricity generated and 
given out is much greater. If a machine of the new type, 
of medium size, with glass cylinders of 40 cm. length and 
about 30 cm. diameter, gives 100, the Wimshurst, with 
plates of 45 cm. diameter, gives only 27, and in some 
cases only 22; while the old Holtz machine, with four 
plates 46 cm., gives 30. But the greatest advantage of 
this new type of machine is that it can be kept in motion 
for three months if necessary, cleaning the glass cylinders 
between the tin strips with a linen cloth only being 
necessary from time to time. After long use the glass 
cylinders must be thoroughly cleaned up and fitted afresh 
with new tin strips and boats, if necessary, and be also 
covered with new varnish. 
The Motor—Any small motor—electric, hot-air or 
otherwise—is suitable to do the little work required to 
move the machine. If an electric motor is used it can 
be battery-driven. Small hot-air motors are suitable for 
this work. The machine, 4, shown in the illustration 
(Fig. 7) has an output of 75th of a horse-power and costs 
about 48 sterling, or, say, $41. It is easily managed. 
The Field —It the purpose is to apply the electricity in 
such a way that the results can be brought clearly forward 
for comparing the yield on two fields, of which the one 
