Fremont journal. [volume] (Fremont, Sandusky County [Ohio]) 1853-1866, 1858-12-03
ueshod Of DrawInE u1orssIsn Line.

w O. G. HItt~
A meridian line drawn on tho noor Of
room, or on any other Fixed horizontal plane,
whero the sun shines, is usoful for many pur-
poses, namely: determining when the sun
is south, or apparent noon when star Of
the moon is on tho meridian; asccrtaining
the correct position Of dial, and even tho
variations Of the compass r
Tho easiest and ono Of the most ccrrcct
rules for drawing il, is as E'lllows: With =
radius Of inches, describe circle on any
permanent smooth, horizontal surface, where
the sun may shine upon it, Mt the center OF
which erect wire one-tcnth OF an inch in
diameter, 70 stand above the surface equal
to the radius, namely: inches, in the fore
noon, when tho end Of tho shadow il obsofs-
ed to fall on the circle, make mark 1t The
touching point. ~. ~ '..l, 'esnl
The coincidence will happen at about 40
minutes past s o'clock, on any clear day ID
June, in or about bolatitudc Of Pittsburgh.
Also, in the afternoon, when the end Of the
shadow again touches the circle, and the
Icoincidence is complete, nnark rs before;
which, under the samc circumstances, will
be noticed about 20 minutes past 8 O'clock.
I A line drawn fiom mark TO mark, win be n
due Fast and West line; another drawn at
! right angles thereto, will be meridian line
, as required. mF
Rendrks.-1. Be careful to have tho
; wire exactly perpendicular; this adjustment
is perfected when the end Of tlic wire meas
I ures the Same distance from every part Of
] the circle; or the circle may be drawn from
: tho end Of the wire as n center .to'g
s 2. Make tho surface Ct the plane perfect
9 lly horizontal; this adjustment may bc
, proven by aid Of aspirit level, or even ofia
: common plumb level. eer aieli
. 3. II two other concentric circles be-
2 drawn, one with a radius half an inch great
5 or, and the other half an inch less, than
that Of the first circle, and the end of the
: shadow marked upon them in tho snme
manner, (which would happen about III
| minutes before and after the times above
| mentioned the three observations would
r provo check 10 each other, and tend 10
greater accuracy; also, if clouds obscure the
: sun when tho end of tho shadow would
1 touch ono circle, the touching point may be
{ obtained on another. - !.
t 4. The month Of juno IS the best time for
i these observations, because at this season
S the variation Of the suns declination, in the
+ interval Of marking the touching points OF
IS the shadow. is so little that no sensible cr
d ror can be made on that account. ste1
Y 5. A meridian line thus obtained, nay
h be transferred to any othcr permanent lsve
d surface, by suspcnding plumb line in the
ir established meridian-(the plummot hang
It ing in vessel Of water TO prevent vibration)
h I--snd at that moment when the shadow N
: tho line at noon is observed TO coincide
l. therowith, draw line along the shadow ot
: another plumb line suspended where the
l. meridian is desired to be transferred. This
n can be done more accurately when the sun
# has south dcclination, because thea the
: shadow Of a short line will bs more extend
d ed, consequently can DO better defined. 80
: @. Method 2.-Suspend two plumb lines
d in tho established meridian, about two feet
s apart, also two others where it is desired 10
n be transferred, to hang as near correct as
Is can bo made by estimation. tho plummets
Is all hanging in water to keep them steady.
! On any clear evening when bright star is
1t observed to range with the meridian plumb
10 lines, the Same moment adjust tho other
: two lines to range with the same star; place
y a straight-edge touching the lines thus ad-
o justed, and draw tho meri 7 IN line required
n Scientific Artisan.