The sun. [volume] (New York [N.Y.]) 1833-1916, 1903-06-21
SCIENCE.
HApIO-ACTIYITY.

In the Contemporary Reriev for May Mr..
Frederick Soddy describes his view OF radio
activity Briefly stated. this is to the effect
that radio active thorium y. which is contained
In ordinary thorium. and can be separated by
precipitating the inactive thorium by means
Of ammonia. Is Il first decomposition-p product
Of the unstable thorium atoms that the radio
active emanations which are transmitted by
thorsum to neutral gases. such as hydrogen
and nitrogen, and which are condensed by
cooling to 1872 G., represent further stage
In the atomic degradation and finally he
suggests that helium-an invariable constit-
uent of radioactive materials-is possibly
the last and sta bic product of the shattered
thorium atoms. According to this view.
which will not be received without an EFFORT
by chemists trained to believe In the conser.
walton Of matter and the immuta ility of the
from the della a grafton Of a minute % and IN.
Vegetable proportion OF the almost explosive
radium atoms.
London, Sir William trookes exhibited OBJ
lects illustrating certain properties Of the
edHnation, Of radipm II solid piece s
screen. and the surface examined with u pocket
lsns sEnfying abou, twenty daetsrs
nearer the screen the .scinthlations become
more numerous and brighter, until when
so quickly that the surface looks like n turbu-
lent luminous sea. A convenient way 70
show these scintillations is to ut the blende
screen at the end OF Il brass tube with speck
Of radium salt in front OF 1t and about Inlli-
metre metre on. and to have lens at the other end
to see Tie bes, efr Sst ~ is done BY lrawins
the lens tube In or out
sExTANr OBSERVATIONS AT SEA.
An artificial horizon attachment to sex
tants. invented by Commander Campbell
Hepworth. c. b., consists essentially OF
contact maker. operated by a plummet
mounted on sextant, and connected with
galvanic battery. 1t is so adjusted as to close
the circuit aud ring bell when slit or line
on the horizon glass is in alignment with the
eye OF the observer and the sensible horizon.
observations for latitude and longitude at
horizon ia obscured by log or mist. although
sun, moon or stars may be shining clearly
but with the aid of this instrument the OBJ
server may obtain the true altitude OF hasy-
emily body within five minutes of arc. This
rough approximation will often be valuable
Sun SPOTS AND EARTH TEMPERATURE.
At a recent meeting Of the French Academy
OF Science a paper was read b. Nj. Oh. Nord-
mann on the period OF the solar spot, aud the
variations OF the mean annual temperature
Of the earth. His discussion Ia founded on
observations obtained at a great number OF
stations during the years 1870 TO 1900. and
is. in fact, a continuation OF that Of koppen.
which depended on those from 1880 to 1870.
As the latter had shown that no regular sue
cession could be traced from observations
outside the tropics. NJ. Nordmann has made
use only Of stations within the tropics OF
which a much larger number are available
than were for his predecessor His concu-
sion is that the variations of mean terrestrial
temperature do undergo period sensibly
equal to that Of the solar spots and that in
crease in the frequency Of spots corresponds
to diminuton of temperature and vice versa.
Koppen found from the long series OF ooser
vations that within the tropics the maximum
of heat usually occurred about a year before
the sun spot minimum. The most striking
correspondence Is that while the interval
from maximum to minimum Of the spots IL
greater than thar from minimum to maximurl.
a similar inequality is manifested in the
variations of temperature.
ROTATION PERIODS OF JrPITER's sroTs.
" is we'll known that spots on the planet
Jupiter have different rotation times accord
ing TO their din erant ATTITUDES During the
FIVE years. ls0s-ln02. the average results
were according to Mr. Denning: