138 Contribution to the History of Electricity, 
take in his public lectures. The students who attended this se- 
cond class, were generally persons of better parts and more in- 
quisitive minds than ordinary ; and being for the most part of a 
riper age than many of the first class, he could with propriety 
Jay aside the dignity of the professor before them, and assume 
the more engaging character of the friend; and that they might 
be induced the more effectually to lay aside all unnecessary re- 
straint, he used to communicate to them any newdiscoveries which 
might be made in any branch of science, and tell them frankly, 
without any species of reserve, the doubts and difficulties that 
might occur to him upon any subject. As this was his constant 
practice, they were not much surprised at his acquainting them 
one evening, that he had just received a letter from a friend of 
his in Holland or Germany (I cannot be positive which of these) , 
containing, as he said, discoveries in natural philosophy, which 
were of such an extraordinary and whimsical nature, that he could 
give no manner of credit to them, and that the only conclusion 
he could draw from the letter of his worthy friend was, that his 
judgment was certainly failing, and that he had communicated 
the reveries of an infected imagination as discoveries in science ; 
that on this account it had given him great uneasiness, as he sup- 
posed he had lost for ever a friend of sound knowledge, from 
whom he had reaped much solid instruction; and concluded with 
some moral reflections on the instability of all human attainments, 
however dazzling it might be, seeing that it might ke so suddenly 
snatched away from them. He then produced the letter, and read 
it to them. : 
The principal contents of this letter were, that lately in the 
neighbourhood of the place where the writer lived, it had been 
discovered, that by turning a glass globe quickly round upon its 
axis, and at the same time rubbing it upon certain substances, it 
was heard to crackle, and seen to emit sparks of fire; that if any 
person touched it at that time, he suffered a violent shock, and 
scemed to have received a violent blow upon the wrists ; that if 
any number of persons were joined together and one of them 
touched the globe, all of them were affected with the same vio- 
lent sensations at the same time; and fire was seen te break forth 
where they touched each other at the same instant; but that if 
these persons in place of standing upon the ground stood upon 
certain other substances, they felt no shock at all when they 
touched the ball; but that if another person standing upon the 
ground touched them at the place where they were touched, they 
felt a sharp prickling pain, and fire was seen to issue from the 
part; that if one attempted to kiss another when standing in this 
manner, they were suddenly repelled from each other by an fo 
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