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MARYLAND GEOLOGICAL SURVEY 435
with him, as there was an alt-azimuth instrument in connection with
the magnetometer. After a few stations had been occupied, the stand
for the dip circle was also discarded, an extra head or top having
been prepared instead, which when fitted on the magnetometer tripod
permitted the placing of the dip circle on it. Thus but one tripod
was needed for the making of the entire set of observations.
BASE STATION.
Linden was selected as the base station of the survey. In addition
to being the home of the observer, it was nearly in the centre of the
area over which the observations were to be made and was moreover
only within a few miles of the Washington Magnetic Observatory
and the Coast and Geodetic Survey office. After some preliminary
investigations had been made at the base station, and the magnetic
elements well determined, I was ready to start out on magnetic trips,
returning to the base station at various times during the period of the
survey.
ITINERARY OF MAGNETIC TRIPS.
In the table below D stands for magnetic declination, J for mag-
netic inclination, H for horizontal component of earth's magnetic
force, and TS for time signals transmitted telegraphically at noon by
the Naval Observatory at Washington over the Western Union tele-
graph wires. These time signals were used to obtain the rate of the
chronometer.
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Date.
1896.
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Station.
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Elements
observed.
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Remarks.
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Sept. 1
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Silver Spring,
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TS
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Two miles from Linden.
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4
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Linden,
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I
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The elements repeatedly determined
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during July and August.
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7
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"
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D, H, TS
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TS received at Silver Spring as before.
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9
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21
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Upper Marlboro,
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D, I, H
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Fine, clear day, moderate wind.
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10
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23
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La Plata,
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D, I, H
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" " " light wind.
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10
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14
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Brandywine,
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While waiting for train to Mechan-
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icsville.
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11
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19
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Mechanicsville,
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D, I, H
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While waiting for stage to Leonard-
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town.
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11-12
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11
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Leonardtown,
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D, I, H
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Weather fine on 11th ; light rain next
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morning.
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1 From station to station in a straight line; for example, La Plata is 23
miles from Upper Marlboro.
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