The evening times. [volume] (Grand Forks, N.D.) 1906-1914, 1912-04-22
SMALLEST THING
ON q WORLD
trechnical World Masazine.)


The smallest thing in the world. an
clcctron. which is minute beyond CON.
prehension. has at last been isolated
n its charge accurately measured.
The man TO do 1t was Prof. r. A. Milli-
Kan OF the Ryerson laboratory. Uni
stands forth as one Of the clevcrest
and at he same time one of the most
! important, achievements of modern
physics.
-, The text books tell us that tho
smallest part Of Il substance that can
exist separately and still retain it's
composition n properties is a mole.
Guile. a molccule is a combination Of
TWO or more atoms of any element
held together by chemical attraction
or ainnltN. An atom. therefore. is
smaller thai a molcculc. But an cleo
tron is very minute eve in COMPARE
son with an atom. for there are hun
drcds OF clcctrons in a single atom Of
most OF the common substances and
the volume actually occupied by these
el%ectrons themselves is probably as
small Tn comparison with the volume
of the atom. as is the volume of the
sun and the planets in comparison
with the whole volume Of tho solar
system.
Scientists have long believed that
electricity was just as definitely atomic
as II other substance mass Of
iron. for instance. Prof. Millikan has
given additional proof of the correct
ness that there is a measurable and ul-
innate limit to the divisibility OF an
electric charge. and has accurately de-
tcrmined the value of the ultimate
electric atom.
An ion is a molecule carrying one
free clcctron. or atom of electricity.
N diameter of Il moleculc is
."0000oO0 of an inch. Ii would
take 1000 molecules laid side by side
iii Il row to make a speck long enough
to he seen in the most powerful micro
scope. The diameter of an clectron is
about M hundred thousandth that of
"A m%olecule. This means that 100. 0o0.-
600 of them would nave to be placed
in a row and then magnitied a thous-
and or more times before the spcck
they made could be seen.
To Illustrate again. lot us suppose
that 100000 900 people began to count
tho number of electric atoms ncccs-
sar% to generate 10y clcctrolysis suf-
iicirnt hydrogen to ill an ordinary toy
balloon. II they counted at the rate
Of 100 Il minute. and kept steadily at
IL, never stopping to cat. sleep or rest.
IL would take these 100. 000. 900 hust-
lers something like 1000, 900 years to
complete the job.
Prof. Millikan has not only solved a
seemingly impossible problem. given
additional proof OF tho atomic theory
of electricity, and shown that a very
satisfactory ocular demonstration is
possible of the perpetual dance of the
molecules of matter, but probably has
made by far the most accurate of all
organizations Of the value of the
fundamental unit. MOI is this all, for
the improved value of this unit also
carries with it CORRESPONDENCE COR
rccted values of other things, such as
the lumber of atoms per unit weight
of any given element. and the mass Of
the unit itself.
The history of tho atomic nature of
electricity which has eliminated in
Prof. Millikan's recon discovery dates
back almost Il century. FaradaN WAS
the first to prove that when an electric
current is passed through q water So
luton of n one of certain substance
es. the substance itself is taken out OF
the solution. The extent to which this
action takes place is dependent upon
the quantity Of electricity SO passed,
and upon the nature Of the substance
dissolved.
1T the same current is passed in Sc
ries through the water solution of
such salts as copper sulphate, sodi-
um sulphate and silver nitrate, the
weight OF the metal deposited, or per-
manently removed from the solution,
10 AiCStS ptopOI tiOIidl W Liz dlOIlIC
weight of the metal itself. and inverse
~ proportional to the number of hy-
drogen atoms necessary chemically to
take the place of one atom of the
metal. Repeated experiments proved
that this proportionately held true un-
der all conditions. and it was there
fore regarded as certain that to each
ion in a solution conveying an cleo
trio current there belongs a definite
electric charge.
The natural inference drawn from
these experiments was that electrical
charges also are definitely atomic in
their nature. For many years, how
ever. there was no way to test this in
ference except in the case of any |
composition Of an elcctrolyte. and
even the most refined measurements |
could directly detect nothing less than
the aggregate of countless millions Of
elementary charges.
Similar difficulties presented them
selves in connection with the so-called
cloud method of determining the cle-
by Sir Joseph Thompson about 12
years ago. This method. with modif-
cations by H.. \. Wilson. consists in OBJ
serving first. tho rate Of fall under
gravity Of a cloud produced In an ion
lied fog chamber. and second, the rate
of fall Of a like cloud when a vertical
electrical field Is superimposed upon
gravity. Here. too. all tho deductions
relating to the elementary charge were
drawn from observations of the aver
age behavior in electrical and CRAWL
rational fields of swarms of charged |
particles. and consequently the value
of the unit charge was not determin-
able.
1t was while experimenting with the
cloud method about two years ago that |
Prof. Millikan succeeded il balancing !
individual charged drops by an cleo
trostatic field. a feat which led direct
ly to his discovery of a way to isolate
an ion.
sisted essentially in catching ions on
droplets of water or alcohol. in then
isolating by a suitable arrangement a
single n OF these droplets. and
measuring its speed first in a vertical
electrical and g%ravitational field COM
hincd. then in a gr%avitational field
alone.
There we're. however, several sourc-
es Of error or uncertainty still attach
cd to this method.
The substitution Of oil for water or
all Of these limitations.
Through the study of the behavior |
in electrical and gravitational fields of
this Oil drop. carrying it's captured
ions, it was also possible to present d.
rect and tangible demonstration Of the
fact that all electrical charges, how
ever produced, are exact multiples Of
one definite. elementary electrical
charge: to make an exact determin- !
alton of the value Of the elementary
charge which is free from all ques-
ti~,no hfA thrs A.