304
DOCS.
402,
403
JUNE
1912
402.
From Paul Habicht
Schaffhausen,
1
June
1912
Dear
A. E.,
Now
the honored
public
will
really buy
the
p[otential]
m[ultiplier]![1]
I've made
a
discovery!
The interferences that
we (I
and the
man working
for
me)
observed
are
electromagnetic
waves.
After
having
sent
your
letter
to
you,
it
occurred
to
me
that
even
though we
had
no
storm
nor
even
sheet
lightning yesterday,
the
atmosphere
was
still
stormy.
The
western
sky was
black. I
rushed
immediately
to
the
large
inductor
at
the
cantonal
school[2]
and found there that
the
fluctuations increased whenever the
spark
gap
was
switched
on.
Unfortunately,
I
was
able
to
conduct the
test
only across
3
rooms,
and
only
for
1.5
min.,
because
Prof.
Gysel[3]
had
no
time. So
now
I
bought
myself an ignition
coil,
which I
got
in
an
automobile
shop.
It
produces sparks
of
up to 10
mm.
I
put up
a
0.5
meter-long
antenna.
The
Maschinchen with
the induction
coil
(the
same one
I
had
in
Zurich)[4] was
set at
a
distance of
5
meters,
and
the
primary
terminal
also
got a
0.5
m
antenna.
When
the
inductor
was
not
switched
on,
the
max.
fluctuation
was
6
scale
divisions,
and the
mean,
2
scale
divisions. As
soon as
the
inductor
was
switched
on,
I
had
full
deflection,
then
0
again,
then
a
position
in
between,
then
0,
then
full,
etc.
Upon
the
switching
off of the
inductor,
immediately rest.
Now,
I went
into the
garden
with
both transmitter and
receiver.
The transmitter
was
connected
to
the
alternating current
circuit. But it still
had
its circuit
breaker. The
receiver
was
totally
by
itself.
It
consists of
a
storage battery
a p.
m.,
an
electroscope,
and
the
coil with
the
0.5
m.
antenna.
Even without
a
ground
circuit
one can
certainly
attain
10 meters
this
way.
But
with
a
ground
circuit I could
...
40
meters
without
403.
To
Conrad Habicht
Prague,
2
June
[1912]
Dear
Konrad,
How
delighted
we were
with
your
momentous
postcard,
which
found
us
today
(Sunday)
still in bed.
Hats
off to
her
who
softened and subdued
such
a
hard-boiled
character.
I
wish
you
and her the
greatest happiness
there
can
be. Come
to
see us soon
with
your
chosen
one,
after
we
have
set up
shop again
in
Zurich
(at
the
beginning
of
August).
Best
regards
to
you
and
her
from
your
Einstein