The morning call. [volume] (San Francisco [Calif.]) 1878-1895, 1893-12-01
ArduOus Task of Professor
Davidson.
TO FIX THE MERIDIANS.
1t Can Only Be Done by Star
Gazing.
SEVERAL HOURS EVERY NIGHT
Making Observations to Reduce the
Variations of the Geographical
Latitude.

II there is one man in the employ of the
Government who is about as greatly inter-
ested In the state Of the sky as Weather
Clerk Pague that one is Professor George
Davidson of the United States Coast and
Geodetic Survey. lie is more than inter-
ested. He wants clear nights, and must
have them. for he has great task to &C.
complish. it being nothing less than an en-
deavor TO reduce the variation of the geo.
graphical latitude.
About one year ago observations were
Instituted by the Association Geodetique
Internationale at the stations in Washing
ton, San Francisco and Honolulu to deter
mine this recently discovered irregularity
in observations for latitude. The United
States is member of the GeodetIc Asso-
citation. and In 1889 the President of the
United States appointed Professor David
son as delegate to the conference at
Paris
AT that time systematic latitude obser-
vations at Berlin, POtsdam and Prague
had demonstrated the existence of a varia-
tion that had an amplitude of about 60
seconds OF an arc, or sixty feet on the
earth'S surface. In other words, deter
mination Of the latitude of boundary line
at one time in 427 days period would
d'lOi oiAty icOt 1IOu eH0 IdtlNuuo az all
other epoch in that period. This and
other practical applications of latitude OBJ
servations, and more particularly the sys-
tematic effect upon all measures of declina-
ton In star catalogues OF the great Obser-
vatOries Influenced the association to
observe the phenomena on broader
scale so as to cover the semi-circumference
of the earth.
The observations at Honolulu and at
Washington have been reduced and nearly
confirm the predictions. Those at San
francisco. numbering as many as the
others. are only partially reduced, but so
lar the results are very satisfactory.
DR.. &. S. Chandler. one of the most inde-
fatigable astronomical investiga tors 10 the
world, examined every available series of
observations made from the time OF Brad
ley Q755), and found two causes for this
variation. each with a different period. and
thereby giving a complex curve of varia.
ton. just as the tides are complexed by
the attractions OF the sun and moon, one
exerting through solar day period and
the other acting through lunar day
period.
The French scientists have attacked the
results and theory of the variation of lati-
tude. Folie, the director Of the Brussels
Observatory, relegates the matter entirely
to mutation Cornu, the well-known phys
icist, attacks 1t as possible exhibition of
errors OF temperature and OF readings of
the level. His reasoning is specious and
unworthy a man of his ability. Helmert.
an able German authority. has easily over
thrown the French positions As mat
ter of fact 1t looks as if some national feel
ing had been brought into this question
which belongs wholly to the domain of
science.
In the exhaustive Investigation of tens of
thousands OF observations by Chandler he
has shown that there is what we would call
on this coast a half-tide In the variation,
and instead of range or amplitude of O60"
variation, there will be range of only Q. 2~
between 1898 and 1894 And as this varia-
ton moves around the earth from west to
east the obscure minimum will occur about
the middle OF Decemb Der of this year. five
months earlier than it will occur in Eu-
rome.
To detect this minimum Professor Day-
idson has Undertaken a series of latitude
observations extending TO the end Of Jan
uary. He observes on every clear night
through several hours. And by observing
the same groups of stars that he observed
at the same season in 1912, he expects TO
detect this obscure minimum within a
probable error of not over to 2h feet,
The work is laborious and the stars 60 pu.
merous that throughout these hours there
are only two intervals that reach nine
minutes.