The New York herald., 1872-11-15
UNITED STATES SURVEY OF THE PLAINS,
POintings Of the Magnetic Needle.
From the Denver News, Oct. 1871

lFfOm the Denver news, Oct.
We are privileged this morning to give the prac-
tical substance OF the results obtained by DR.. +. c.
Hilgard, formerly OF st. Louis, who Is conducting
the Bache magnetic survey OF the states and Ter
rit0res. This important survey is carried on under
the joint trlsteeship OF the Smithsonian institu-
tiOn the United States coast survey and Professor
l. Agassiz, on the scanty proceeds OF the legacy OF
Professor Bache, the late superintendent OF the
United states Coast Survey.
Proceeding from G0lconda, on the Ohio River, in
Southern Illinois, in October, 1871, the survey was
carried through the northern line OF the ohio
States, by Vincennes, indianapolis, Richmond, In
diana Columbus, ONO, to near " the neutral line"
the pointing Is due north.
1t ought to be at once understood that in all
through Eastern Ohio and North Carolinaj the
pointing OF the compass needle is westward and
west OF that line eastward The neutral line has
been steadily travelling from Annapolis In 1901, to
Raleigh N. G., in 1s7O and s at present moving
westward at an increased rate.
the Mississippi Valley, through New Albany, near
Memphis corinth and oxford, Miss. Grenada
Baton Baton Rouge, New Orleans, the splaaaemines
plantations, and the mouths OF the Mississippi
river o4hwest NV Pass and rass poatre
east-was about 0nehalf degree less than had
been anticipated from the scanty data OF q few
magnetic observations having only been carried
out along the Atlantic. Gulf, and Pacific coast as
incident to the operations proper OF the United
the late superintendent having personally en-
gagged In q series Of inland magnetic observations
the proceeds OF his legacy for the prosecution Of
scientific observations in general, on an extended
scale.
1t ia fact worthy of notice, that in the axis Of
the Mississippi Valley the lines of equal variation
castor 'isogOnic lines,n run nearly north and
south; SO that New Orleans and the city OF st.
Louis, Mo-, have about the same pointing-seven
degrees east. On the Pacific shore, on the con-
trary, and inland, the lines Of equal pointing run
the Intervening tract, inclusive OF Missouri
Kansas and Colorado, remained essentially unex-
The funds having been deficient DR.. Hilgard
pushed the survey thus far on private means;
but was aided by the lberalty OF the st. Louis
Denver and Rio Grande railroad companies;
from st. Louis to Herman, Mo-; Sedalia, Kansas
City. salina, Enis, Wallace, Denver, and
Pueblo, with q view to carrying the same to
Hughes, Boulder and Cheyenne &c. At the for
mer places, as well as at Dubuque, Iowa, Wenona,
Macon and Highland, Ill., and at Cairo. Ill, CORE.
spending observations were taken and at most
places meridian or true noon line was determined
within the limits OF instrumental accuracy.
In order to make the following data, for which
we are indebted to Dr. Hilgard, practically avail
able due regard must be had Of the trend OF the
isogonic lines; by which, for example, San Diego
line as Wallace, Colorado; and Pueblo about
threef fourths or degree east lin pointing) OF
Denver. The dip of inclination OF the needle, or
rather of the magnetic force when free to act, is
likewise subj0ined, ninety degrees meaning the
vertical. The eliminating vortex of the magnetic
current, or the so-caed magnetic pole, Is at pres
ent assumed in Bo0thla Felix, on the polar circle.
II will thus be understood that while the neutral
line was once at Cleveland, OniO, the pointing at
Boston was eleven degrees west, and at Victoria,
vancouver's Island about twenty-three degrees
eastl
In the following table the variation given implies
the mean variation OF the whole twenty-four hours
that very uniformly takes place at about six O'Clock
r. M. The range OF daily variation, it is well
known, between seven O'Clock In the morning and
hottest u
ally amounts to from ten to eighteen minutes OF
angle. Keeping all these facts in mind the follow
ing table OF results will be found generally useful
to surveyors and travellers, especially in the plains
Places. variation East Din.