DOC.
23
COMMENT ON DOC.
13
111
Doc. 23
Comment
on
Our
Paper:
"Experimental
Proof
of
Ampere's
Molecular Currents"1
by
A. Einstein and W.
L.
de Haas
[p.
420]
Our
colleague
Berliner
recently
sent
us
two notes
by
S. J.
Barnett
that
were
[2]
published
in the
July
30,
1915,
and
October,
1,
1915,
issues of Science. From these
[3]
it is
plainly
obvious that
Maxwell
already
had the idea to look for
gyroscopic [4]
properties
of
magnets
in order to test
Ampere's
hypothesis.
Barnett
writes: "The
experiment
which
I
recently
described
in
this
journal
can
be
viewed
as
a
modification
of
one
undertaken
a long
time
ago by
Maxwell,
who
seems
to have been the first
one
to think that
a magnet
must act like
a gyroscope
if the
Ampere
currents
are
of
a
truly
material
nature,
as
modern
theory
assumes."
[5]
Barnett
began
his
experiments already
six
years ago,
and
now
says
that
positive [6]
results have been achieved. He tried to demonstrate those
magnetomotoric
forces
which
occur
in
an
iron rod that is in
rapid
rotation.
Experimentally,
this
problem
is
[7]
incomparably more
difficult
than
the
one
undertaken
by
us,
which is to
verify
the
angular
momentum
that
occurs
due
to
a change
in
magnetization.
Mr.
Barnett's
and
our own experiments complement
each other in
a
gratifying
manner.
1Verh.
d. D.
Phys.
Ges.
17
(1915),
p.
152.
[1]