Herald of the times. [volume] (Newport, R.I.) 1830-1846, 1838-07-26

l should have added that throughout his
whole oraiion he did not once allude to the
lllustgious Hero Of two wGrs, the Greatest
aud Best, the Vencrated Chief, General Jack
son, nor the Smallest and Meanest, who pro-
fcsses TO follow in the footsteps Of his illus
rrious predecessor, any more than f such be-
ings had never existed. lie probably thought
he could say nothing in their praise, and
| therefore it was The most discreet course to
II pass them over in silence.
II
n From the n. Y. Commercial Advertiser.
II DR SHERwooD's DIscovERY.-We arc in
dcbied to friend at Washington for copy
Of Mr.. Tallmadge's report COMMITTEE Oh
naval afairs) upon the memorial Of Henry
Hall Sherwood, Of this city, claiming to have
discovered a means Of ascertaining the lon.
gtndc, &c., nnd praying the aid Of Congress.
The report itself is very short, and merely
serves as introduction to various documents
set forth. These discoveries are certainly
of The highest importance, and if we could
spare The room we would gladly quote the
long letter OF Dr. Dwight, in which they are
set forth; but under existing circumstances
we must content ourselves with such extracts
rs will suffice to give our readers a correct
ilca Of the great results which DIR. Sherwood
II claims To have effected.
Having succeeded, after many years Of
experiment, in magnctizing n continuous
iron ring, and circular iron pate-hercto.
fore deemed impossiblc-Dr. Sherwood, by
their means, was enabled 10 ascertain the
true magnetic pole. magnetic axis and mag
nctic cquator-as set forth in the following
quotation.
| This conclusion led To the most important
results. lie was hence led To sec that the
magnetic poles OF the earth were 23o PSI
from its poles, and of course in the polar cir |
clcs; that the magnetic and polar axes eros
scd each other at the same angle of 23o 28.:
aud that the magnetic and terrestrial merid- |
ans OF every place crossed each other at an
giles dependent on the angles OF the two
axes.
| 1t had been believed by various philoso-
piers, that the magnetic poles have rcvo-
luton round the poles Of the earth. DR. Sher-
wo I'd ascertaincd, from observations made at
i London and Paris more than century AMI a
half ago, that the line or circle of no r0ria-
II lion was in two given years, not distant from
each 0tbe-, over those cities. lie found also
numerous records of its being over other
places in lis progress westward, at certain
other given periods. lie also nscertained
its exact present position, in various places
on the western continent. Bya careful com.
II parison of these varions results, he ascertain.
ed, lst. That the circle Of no rayiaiion, and
. Sh., s,nla bal
western progress /; and 2dlv, That they re
voIved in period o. GG6 years. and Of course
had an annual motion OF 3G0S
G66
Having ascertnined the line of no rariaiion
and its exact rate Of progress, he was Of
course enabled, after obtaining its true posi-
lion on any given day and at any one given
place, TO trace its progress round the earth,
and determine its exact longitude in any
latitude. What followed is thus stated in
Mr.. Dwigh's letter.
Il These principles and positions remained
TO be tested by mathematical demonstration !;
a task. obviously, Of great difficulty. TO nc
II lcOnplish il, il was necessary to construct
Il series OF irisonometrical tables, depending
on the great principle that the magnetic
poles and the circle OF no variation have these
exact positions, and founded on the angles
which the circle of no variation and all the
other magnetic meridians make with the geo
graphical meridians in every place on the
globe, as well MS on those which the magnet
ic equator makes with the terrestrial equator,
and with the geographical mcridians. Nor
was this all. IS all these angles, except
that between the two equators. owing to the
revolution Of the magnetic poles, and to the
consequent revolution of The magnetic me-
ridians, are continually changing, it was also
necessary to form another series Of tables,
by which an exact allowance might be made
for these changes, in determining the exact
position Of the various places on the surface
Of the earth. To do all this, and so to do il
iIpt the results should always be attended
with mathematical Certainly, required very
high powers Of comprehension. analysis, and
construction. To this task DIR. Sherwood
Il applied himself and formed the requisite
tables on these principles. To render these
| principles of universal practical utility, DIR.
H Sherwood devised and constructed an in.
H strument which he deuomnates "rHE GEoME-
TER"
II The powers Of this instrument are descri
bed as follows:
II With the correct dip given him, observed
at given time, ho works out either or oil Of
the following results: The variation Of the
needle, the distance Of the circle Of no va
ration from the place, and its angle with the
meridian, the latitude, and the longitude
II With the variation given hun, in the same
manner, Inc determines the dip and the other
results.
II With either the dip or variation correctly
II given, he also determines whether the obscr-
we'd dip or variation, and the observed latitude
and longitude, are correctly observed, and
riee rersa. lie must know. however, if the
dip be given, whether the place Of obscrva.
ton is east or west Of the circle Of no varia.
ton, and, il the variation be given, whether
II is north or south Of the magnetic equator,
and near the artic or aniartic semi circle Of
no variation, points which would always and
of course be known. in the practical use Of
the geomeicr. lie mnst also know the time
| of tie observation. Bv means of one Obser-