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thetically imagined as existing between them, is nothing; 
and, as nothing , it can have nothing to do with the conduction 
of the electricity. The entire argument, therefore, of this 
truly great electrician goes for nothing, so far as his reasoning 
from continuity in “ space ” is concerned. 
There is one part of the argument, however, which calls for 
a separate notice. He founds this upon the statement that “ a 
space which can contain 2,800 atoms, and amongst them 700 
of potassium itself, is found to be entirely filled by 430 atoms 
of potassium, as they exist in the ordinary state of that 
metal.” On the ground of this statement he founds the con- 
clusion that there must be far more space than matter in 
potassium ; c> r yet it is an excellent conductor.” So he says 
again, “ space must be a conductor.” But we say also again, 
that there is no such “ must he ” in the case. The necessity 
of truth is in the opposite direction. Space, which in the 
absence of a substance is nothing, cannot be either a conductor 
or a non-conductor. The particles of potassium pass into a 
state of electrical agitation on the sufficiently near approach of 
electrically agitated matter — -just as the particles of water 
become agitated when the wind or tide approaches, and the 
particles of the massive rock are still — that is the fact as demon- 
strated by experiment — the space in which they are agitated 
having neither more nor less to do with the conduction than 
the space in which the experimenter himself moves has to do 
with his movements. 
There is, however, another notable idea in this remarkable 
letter of Faraday. He shows that “the volume, which will 
contain 430 atoms of potassium, and nothing else, while in the 
state of the metal, will, when that potassium is converted into 
nitre, contain very nearly the same number of atoms of potas- 
sium, i. e., 416, and also then seven times as many, or 2,912 
atoms of nitrogen and oxygen besides.” He gives another 
instance of the same thing in another substance, and refers to 
many others, all proving that a vast number of atoms may and 
do occupy the space which seems full with comparatively few. 
He is foreshadowing in these statements that in which the 
wildness of his speculation is most effectually seen — his denial 
of the mutual impenetrability of matter. His theory, after 
Boscovich, is that atoms are not particles of mutually impene- 
trable substance, but “ centres of force,” to which centres 
there is neither length, breadth, nor thickness ! They are 
merely “mathematical points,” and need no space for their 
accommodation ! Space according to this idea is not even a 
requirement of material existence ! Strictly these centres of 
force are nowhere ! That which occupies no space is simply 
