UNDER THE APPLE-TREES 
conception, as it is beyond the power of conception 
of the best of us. Yet we have to accept the atom 
on the demonstrations of experimental science. The 
helium atom has been proved to be an objective 
entity as truly as is the sun in heaven. The apparent 
contradiction of an indivisible body is involved in 
our habits of thought formed by our dealings with 
ponderable bodies; we are introduced to the world 
of chemical reactions. We cannot conceive or pic- 
ture to ourselves just what takes place when two 
gases unite chemically, as when hydrogen and oxy- 
gen unite to form water. Our only resource is to 
apply to the process mechanical images; our experi- 
ence affords us no other. 
We fancy that the difference between two com- 
pounds with the same chemical formula, but with 
widely different properties, —say alcohol and 
ether, — consists in the different arrangement of the 
particles. Arranged in one order, they produce one 
compound; arranged in a different order, they result 
in a compound with different properties. Yet every 
particle of these gases is supposed to be exactly like 
every other particle. How hard, then, to conceive of 
any mere spatial arrangement of them as resulting 
in such widely different products. One has to think 
of each atom or electron as a little world in itself, 
containing different stores of energy or vibrating at 
a different rate of speed, in order to see substances 
of such different properties arising out of the differ- 
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