DOC.
3
31
whose
coefficients
are
arbitrary
functions of the
p's.
Two
kinds
of
external
forces
shall
act
upon
the
masses
of
the
system. One
kind of force shall
be
derivable from
a
potential
Va
and
shall
represent
external conditions
(grav-
ity, effect of rigid walls without thermal effects,
etc.);
their
potential
may
contain time
explicitly,
but
its derivative with
respect to
time should
be
very
small.
The
other forces shall
not be
derivable
from
a
potential and
shall
vary
rapidly.
They
have to be
conceived
as
the
forces
that
produce
the
influx of heat. If
such
forces
do
not act,
but
Va
depends
explicitly
on
time,
then
we
are
dealing
with
an
adiabatic
process.
Also,
instead
of
velocities
we
will introduce linear
functions
of
them,
the
momenta q1,...,qn,
as
the
system's
state
variables,
which
are
defined
by
n
equations
of the
form
dl
qv=Wv'
where
L
should
be
conceived
as
a
function of the
p1,...,pn
and P1',...,pn'.
§2.
On
the
distribution
of
possible
states between
N
identical adiabatic
stationary
systems,
when
the
energy
contents
are
almost
identical.
Imagine
infinitely
many (N)
systems
of the
same
kind
whose
energy
content
is
continuously
distributed
between
definite,
very
slightly
differing
values
E
and
E+
SE.
External
forces that
cannot be
derived
from
a
poten-
tial shall
not be
present,
and
Va
shall
not
contain the time explicitly,
so
that the
system
will
be
a
conservative
one. We
examine
the distribution of
states,
which
we assume
to be stationary.
We
make
the
assumption
that
except
for the
energy E
=
L +
Va
+
Vi,
or a
[5]
function of this
quantity,
for the individual
system,
there
does
not
exist
any
function of the
state
variables
p
and
q
which remains
constant
in
time;
we
[6]
shall henceforth consider
only
systems
that satisfy this condition.
Our
assumption
is equivalent
to
the
assumption
that the distribution of
states of
our
systems
is determined
by
the
value of
E
and
is
spontaneously
established
from
any
arbitrary initial values of the
state
variables that satisfy
our
condition
regarding
the value of
energy.
I.e., if
there
would
exist for the
[4]