CHAP TERR i 
THE CONSTITUTION OF MATTER 
S| Mle atomistic conceptions of Leucippus and 
Democritus have acquired new interest owing 
to the results of modern experimental work concern- 
ing the constitution of matter. All substances, they 
taught, were primarily formed of atoms too small 
to be apprehended by the senses: indivisible and 
unchangeable, though differing greatly in shape and 
size. [hese atoms were supposed to be constantly 
in motion and separated ‘‘ by avoid.” The qualities 
of different bodies were thought to be due in part to 
the kind of atoms existing, and in part to their 
arrangement in the bodies in question. Aristotle 
put it thus: ‘‘ Democritus and Leucippus say that 
all things are composed of indivisible bodies, and 
that they are infinite both in number and in their 
forms, and that the differences between things are 
due to the elements of which they are composed 
and to the position and arrangement of these 
elements.” 
Such views were, of course, mere speculations 
having no basis either in observation or in experi- 
ment. But, like the modern “ Atomic Theory,” pro- 
mulgated by Dalton in the early years of the last 
century, these speculations rejected the notion of 
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