15.
COSMIC RAYS
343
increase.
It must be conCluded that the ions are created by a
radiation originating outside the chamber and capable of pene'
‘
trating the metal walls. That a part of the natural leak is due to
gamma rays from radioactive substances of the earth can be
demonstrated 2 by placing ice or lead, free from radioactive contamina—tions and of great thickness, under the electroscope and
"
also by surrounding it with several inches of lead. The natural
leak is reduced but not entirely eliminated. It is obvious that
…
the residual lea/«, which is observed after correction of the natural
leak for local radiations, must be due to a very penetrating form
"
of radiation.
In 1910, Gockel3 measured the residual leak of an -electro_
‘
scope
at different heights up
to 4500 meters above the earth’s
surface, with the aid of balloons, and found that it increased_
_
slightly at the higher altitudes. Hess,4 in 1911 and Kôlhôrster,5 —
'
in 1913—1914, extended the obServations to 5200 and to 9000
meters, respectively, and found an increase of as much astWelve
'
times the sea—level value.
The penetrating radiation Which pro__
duced the residual leak must then indeed have
at a
_
great distance above the earth’s surface.
,'
—
—
_
_
It was Hess in 1912 who rst denitely ascribed these effects
.
_
to radiation coming from beyond the atmosphere.
_
_
In 1924, Millikan and his cœworkérs“measured the‘absorption
‘
'
.
penetrating rays by lowering an electroscope to different
depths in each of two lakes at dierent altitudes. TheyÆ0ùnd that _
some of the radiation had sufcient penetrating POW€Ÿ
pass
through the entire thickneSs of_the earth’s atmospherÿg—”SÊVËŒl
‘
’
times and, further, that the layer of air betWçÇ, the higher and
'
’
lower lakes did not contain sources" of
_
source of the ionization is,‘
IÏÏ
;
absence of any known mechanlsmf01'Pmdu‘ïmgsuCh€XCŒdmgly
,
penetràting raysin the upper atrnosph‘îf‘î}MlHlkancol
'
ÏÎhe radiation came from beyondthe©11ŒTmOStboundar Y;th
eari’s
5 ‘
-
?
_
.,
It is now known that theradlatlOnœaChesag1V€npomt
the
.
_
é'aTth’s sr'1rfacein‘:essent1allyconantamount(imperœm)’day
—
COSMIC RAYS
343
increase.
It must be conCluded that the ions are created by a
radiation originating outside the chamber and capable of pene'
‘
trating the metal walls. That a part of the natural leak is due to
gamma rays from radioactive substances of the earth can be
demonstrated 2 by placing ice or lead, free from radioactive contamina—tions and of great thickness, under the electroscope and
"
also by surrounding it with several inches of lead. The natural
leak is reduced but not entirely eliminated. It is obvious that
…
the residual lea/«, which is observed after correction of the natural
leak for local radiations, must be due to a very penetrating form
"
of radiation.
In 1910, Gockel3 measured the residual leak of an -electro_
‘
scope
at different heights up
to 4500 meters above the earth’s
surface, with the aid of balloons, and found that it increased_
_
slightly at the higher altitudes. Hess,4 in 1911 and Kôlhôrster,5 —
'
in 1913—1914, extended the obServations to 5200 and to 9000
meters, respectively, and found an increase of as much astWelve
'
times the sea—level value.
The penetrating radiation Which pro__
duced the residual leak must then indeed have
at a
_
great distance above the earth’s surface.
,'
—
—
_
_
It was Hess in 1912 who rst denitely ascribed these effects
.
_
to radiation coming from beyond the atmosphere.
_
_
In 1924, Millikan and his cœworkérs“measured the‘absorption
‘
'
.
penetrating rays by lowering an electroscope to different
depths in each of two lakes at dierent altitudes. TheyÆ0ùnd that _
some of the radiation had sufcient penetrating POW€Ÿ
pass
through the entire thickneSs of_the earth’s atmospherÿg—”SÊVËŒl
‘
’
times and, further, that the layer of air betWçÇ, the higher and
'
’
lower lakes did not contain sources" of
_
source of the ionization is,‘
IÏÏ
;
absence of any known mechanlsmf01'Pmdu‘ïmgsuCh€XCŒdmgly
,
penetràting raysin the upper atrnosph‘îf‘î}MlHlkancol
'
ÏÎhe radiation came from beyondthe©11ŒTmOStboundar Y;th
eari’s
5 ‘
-
?
_
.,
It is now known that theradlatlOnœaChesag1V€npomt
the
.
_
é'aTth’s sr'1rfacein‘:essent1allyconantamount(imperœm)’day
—