will always succeed perfectly well if both bodies are sufficiently
electrical."(1)

As we now know, Dufay was wrong in supposing that there were two
different kinds of electricity, vitreous and resinous. A little later
the matter was explained by calling one "positive" electricity and the
other "negative," and it was believed that certain substances produced
only the one kind peculiar to that particular substance. We shall see
presently, however, that some twenty years later an English scientist
dispelled this illusion by producing both positive (or vitreous) and
negative (or resinous) electricity on the same tube of glass at the same
time.

After the death of Dufay his work was continued by his fellow-countryman
Dr. Joseph Desaguliers, who was the first experimenter to electrify
running water, and who was probably the first to suggest that clouds
might be electrified bodies. But about, this time--that is, just before
the middle of the eighteenth century--the field of greatest experimental
activity was transferred to Germany, although both England and France
were still active. The two German philosophers who accomplished most at
this time were Christian August Hansen and George Matthias Bose,
both professors in Leipsic. Both seem to have conceived the idea,
simultaneously and independently, of generating electricity by revolving
globes run by belt and wheel in much the same manner as the apparatus of
Hauksbee.

With such machines it was possible to generate a much greater amount of
electricity than Dufay had been able to do with the rubbed tube, and
so equipped, the two German professors were able to generate electric
sparks and jets of fire in a most startling manner. Bose in particular
had a love for the spectacular, which he turned to account with his new
electrical machine upon many occasions. On one of these occasions he
prepared an elaborate dinner, to which a large number of distinguished
guests were invited. Before the arrival of the company, however, Bose
insulated the great banquet-table on cakes of pitch, and then connected
it with a huge electrical machine concealed in another room. All being
ready, and the guests in their places about to be seated, Bose gave a
secret signal for starting this machine, when, to the astonishment of
the party, flames of fire shot from flowers, dishes, and viands, giving
a most startling but beautiful display.

To add still further to the astonishment of his guests, Bose th