Faraday as a Discoverer. 199 
the moment on its surface jointly with the air and surroun 
conductors, then I venture to anticipate that the middle spark 
would be more retarded than before. And if those two plates 
were the inner and outer coatings of a large jar or Leyden bat- 
tery, then the retardation of the spark would be much greater.” 
This was only a prediction, for the experiment was not made.* 
Sixteen years subsequently, however, the proper conditions came 
into play, and Faraday was able to show that the observations 
nal portion of the wire at the first instance, and disposed for 
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acts by induction, Without this reaction of the walls upon 
the sphere you could no more, according to Faraday, charge it 
with electricity, than you could charge a Leyden jar, if its 
er he . . 7 > 
of magnitude ; and if you abolished the walls of the room—even 
the earth itself—he would make the sun and planets the outer 
Coating of his jar. I dare not contend that Faraday in these 
Memoirs made all his theoretic positions good. But a pure 
vein of philosophy runs through these writings ; while his ex- 
periments and reasonings on the forms and phenomena of elec- 
“teal discharge are of imperishable importance. 
Rest needed— Visit to Switzerland. 
The last of these memoirs was dated from the Royal Insti- 
tution in J une, 1838. It concludes the first volume of his 
m * df Sit Charles Wheatstone could be induced to take up his measurements once 
* (ore, varying the substances throu which, and the conditions under which the 
current j ; * ‘ tic and 
experimental eee he might render great service to science, both 
