. By means of the switch
these plates could be charged, the one positively and the other negatively, by making them the terminals of a 10,000-volt storage battery
, while throwing the switch the other way (to the left) short-circuited them and reduced the field between them to zero. The oil droplets which entered at
were illuminated by a powerful beam of light which passed through diametrically opposite windows in the encircling ebonite strip
. As viewed through a third window in