The Helena independent. [volume] (Helena, Mont.) 1875-1943, 1890-07-16
What the United States Coast and
Geodetic Survey Corps is
Accomplishing.
A Survey That May Take Five
Hundred Years to Com
plete.
Its Quiet Working-A Canvas Observatory
in Helena Whore Observations are
Made.

tent which is pitched in the northwest
corner of the Assay Office lawn. And no
doubt some wonder what the large black
letters mean which are painted on the side
of the tent toward the street. The tent
belongs to the United States coast and
geodetic survey. Mr.. st. Clair, Of that
that corps, was IN the tent last evening and
explained the objects of the survey. The
work has been going on for good many
years, and it is estimated that at the pres
ent rate of progress at which 1t is being
carried on it will take between four and
five hundred years to complete the survey.
But when it ia completed Uncle Sam will
have map of his country of which he
may we'll be proud. During the course OF
the survey points will be established in the
various states that will enable them to Sc
cure an accurate survey of their own do
main. The state surveys may then be fur
ther extended and made to embrace
the smallest Typographical features de-
sired. Cities, villages "a and o:t farms as
these surveys, thus rendering boundaries
fixed and secure. The city engineer of
Helena, say five hundred years from now,
may be able to have map of the town in
his possession that will enable him to do
accurate work. If he desires to lay out
line of sewer pipes he can do it without go
ing to the trouble of making an extended
survey, and he will not have to run up to
the county clerks Office and search through
the musty old tones for some old plat of so
and SOS addition to the soriginal town site
of Helena. It may be that BY that time the
city council will have found the services of
a city engineer unnecessary.
In the center of the tent is small brick
pillar sunk into bed of cement three or
four feet beneath the surface of the lawn.
On this pillar is mounted small telescope
OF the best manufacture that Uncle SANS
money, can buy. Through slit in the roof
of the tent the telescope has q clear sweep
of the heavens on north and south line.
The smallest change in temperature will
cant the instrument from ono side to the
other of this established line, and to correct
cope Mr.. Sinclair uses delicate spirit
level which will show the elightest
deviation in the position of the telescope.
Yet in spite of every precausion that is
used instrumental errors will creep into the
work, but they are SO small that they make
but little difference in the results. Mr.. st.
Clair's canvas observatory is connected by
telegraph with another observatory at Salt
Lake, where another member of the coast
survey is working in conjunction with Mr..
st. Clair. On one side of the tent is list
Of twenty stars. With big =. ohiono%etes % net At At
tiny point of light is due. Then with his eye
to the telescope and one hand on an electric
button that breaks the circuit in which is
placed another chron0meter, which records
the divisions of time on small cylinder
moved by clockwork, he waits for the star
off by minute lines, the middle one Of which
is the established north and south line. As
the star crosses each line the electric button
is pressed and the record of the time is
made on the revolving cylinder.
The record aS is made ; on % Cylinder re-
cred with sheet of paper, upon which q
pen traces line interrupted or detected for
an instant, through the agency of an electro
magnet, every time the ohronometer ticks,
and, in doing so interrupts the circuit. The
pen is at the same time moving so that the
line, which Ia thus graduated into spaces
corresponding to seconds of time, is de-
ecribed with uniform velocity. When any
instant of time is to be recorded, the OBJ
server presses the electric button which
breaks the current and causes mark to be
made on the record; the position of which
can be read off with great precision. BY
comparing the observations of both stations
the mean result will give the longitude.
Each evening the two records obtained at
Salt Lake and Helena are compared to at
tain this result.
UAAs Dts OlhlE CAA0 xIOA4 0eSAv A0Ao q low
days ago where he was engaged in the
work. While he was there the Salt Lake
observer was here. These changes of
station are made by the observers in order
to eliminate personal errors as far as pos
eible. During the day the observer is busy
tions from the data secured the evening
before. Last night when Mr.. st. Clair was
called upon the weather was not favorable
for the work. The sky was clouded and
some Of the early stars could not be seen.
In all geodetic surveys the first operation
consists in measuring to the last limits of
accuracy one or more distances called base
lines. These are from five to seven miles in
length and are connected by the processes
of triangulation with a multitude Of points.
SO taken that the lines joining them shall
constitute network of triangles extending
serve as points of reference, to which other
points are referred. The latter points in
I turn serve as starting points from which
the more minute filling up of the survey is
completed.
England has not only covered the British
Isles by the geodetic operations of the
Ordnance survey, but has executed still
more extensive surveys in India, besides
extending at the Cape of Good Hope the
arc first measured by the French. In Rus
sia the geodetic operations cover range of
twenty-nine degrees of latitude. North
America early Iurnlsneu COutIiOutlon TO
the general stock of information on geodesy
by Mason and Dixon's measurement of the
line between Maryland and Delaware, and
the determination of latitude at its terminal
points.
Killed by Posse.
MERRouGE, La, July 15.-Sunday night
twenty-five colored laborers left Heffners
plantation, near Oak Ridge, to make their
way into Arkansas. They were pursued by
posse gathered by Heffner and found this
agreed to return, but when the posse went