New-York daily tribune., 1851-08-27


diaus. Between TIE equator and poles, the lime re-
CURED for the pendulum 20 make go degrees wares
according 20 the iaftuQe being greater the IAilIti
from the pole. NOr these Intermediate l-lltules 'Ae
problem j. well exhibited Oh globe
Having a plcbe iO- the tr-l. - ec. Tor l S'alte-
latitude &c, and app the prncp4e iha. ne ~
vibration IS constant. notwithstanding 'nc leeo--
ton Suppose the plane of VII ration % Je si1C M
dian Of Gr6fnvich draw seres Of lines across the
lara lei Of SGo, parallel 70 tns meru'ah eAuL o.
these ines Will show prec.sc!y tne pOsiOh OF we
yenduum, ~ the revolution. a. the polnt "'tfe 'le
Ire lntersec,s the parallel OF latitude H. iofeKin
ple We draw one ~ these parallel hnes across ne
IntersectCn Of go with the rSf merriam cT i east
Of Greenwich another across the intersection OF the
paralel OF 30 with the sec2Hd meridian another
acyoss the fifrf, and so each VII n sr. the posi-
,on of The plane Of vibration after revolution OF as
many degrees included petWeen the ~ rlllals
{ Ontlnuing tins on, the parallel lines become more
and more eastery and finally ;hey are exactly east
End west IN longitude lsO or IN other words the
plane OF vibration, which IS still parallel 10 the Ieth
Wich mend.an, l. actually al Tent angles 20 te mt
Yldan Of le1- this plane has therefore chdIyf1 a,-
parently 90 while the earth was revolving leJ, or
making halfits circuit. And II this be continued, II
Will be found that the parallel lines viii make the
whole circuit OF SoC' IN teloe the earth feVoiuoh'
or what IS equivalent, IN 45 hOuTs
These parallel lines drawn on the gloDe i IS 70 oe
Observed, should be parts OF great circles, ana are
strictly parallel to one.anoheT Only al the itersec-
tons Wiih the parallel OF latitude. like the merldans
where they cross the equator Their tango nS at taese
intersections viii be actually parallel throughout,
Ike the taneens 10 the mendlans Al the equator and
these tangenis represent the true angle OF the plane
Again take latitude zoe, and in the same manner
draw lines parallel to the meridian of Greenwich,
going eastward These parallel llneS VIII rapidly
oIycree from the meridian. the divergence Deing
nearly O. degrees for every 0dcgees OfOngltude IN
Ion 95 '46 f. the ntersectng line VIII point east ana
west, having made 90 IN ts apparent revolution In
1871 33 II VIII have mace ieo ana IN @s5 lOr 20
east Of the meridian Of GTeenWlchl II VIII have com
pletedthe whole 800 so that M lat 10 the me OF the
apparent revolution Ofthc plane OF ylDrauonls lttlc
over 25 hours The globe thus EXHIBITS 10 he eye the
actual uniform position Of the plane OF vioratlon ana
at the same time its apparent revolution. by mIhng
these parellel lines al one end with an arrow head,
and also describing al arc WIN the point oi inter
section as a center, the increasing divergence from
the meridians, and the apparent rotation by east,
south and west tOnOrih, = well shown.
Ifnow tangonts be supposed to be crA"n 20 each
meridian circle at liz intersection with any parallel
OF latitude say that of 10- these anGenis VIII inter
sect al point IN the axis OF ne earih exended and
the angle included between any two sjc tdngenlsls
the ample which TIE corresponding inertlans make
with one another IN the given latitude me pane
Of vibration. since il continues p.rdel 10 ltSCn, VIII
Therefore chance with reference 10 tie morIdldnS,
iust the amount ofthe angie included between these
iangcHts. THIS Isreadlly seen on the globe marked
on as above explained. III which The Greenwich me-
ridlan j. the saIlIngpoint. The angle winch one OF
the paIailts lines drawn on the globe COR rs tangen
makes with tie meridian II mieTsecis j. IRON the
nature OF parallel ines equal to the angle between
the tangent 10 tins meridian and ihdt oi 6feeh"lch.
The sum therefore Of the angles between al me
tangcnts to the mCrlClans, VIII be the amount OF APP
parent variation II the plane OF Vibration for 81 hours
These tangcntS-WhlCh are strictly The co'dngonis
OF latitudo-ioTm together the surface OF "A cone
whose base ls tic parallel OF latitude and whose
angie Of surface at summit IS equal 10 the revolu-
ton OF the pendulum IN - hours. Il TINS cone DE
supposed 10 he cut open and lard Cut on dl plane.
II VIII form sector OF circle whose angie al thc
center equals the angle around the apex OF the cone
The radius OF this sector (Or Of ats crce equals the
Coiaugort Of latitude, (cot H. and the clrcunfeT
enCc Of the sector IS actually parallel OF latitude
parallel of latitude having been the base OF the
supposed cone. Now, as the number OF degrees IN
any arc ysnos with the length OF the are as related
to The radius of the circle, or as and since the
arc here is parallel of latitude, and these parallels
vary with the cosine of latitude, (coS. h. and since
also the radius ( equals cot Lit follows that the
number Of degrees III the are tor Tie number eX-
pre- sing the apparent motion OF the plane OF vbra-
ton for "a hours) viii vary as 7o7 an expression
equiyaon, to the siHe OF latitude.
OthCr demonstrations arrive at the same result
DuI none Is more simple or more conclusive
The theory thus involves no necessary considera-
ton of The forces engaged but may be treated hs
simply a pCOmCiucal problem, based on the position
of the mcrdlanS of revolving sphere, ana the iac
that the pendulum moves IN 4 hXed direction, para
lei TO the meridian III which II Is started.
The Fg6ct of The Heat Of me sun upon the Prpendcu
iortty u Bunker HH Monument.
BY rRof. HoRsFoRD, OF HARVARD
soon after the PonCulum was placed IA bunker
Hill Monument IT was observed that the ball when
at rest was not always over the same point IN the
fkor The careful consideration OF all The cond-
OnS OF tins fact resulted ln aScrlbmg 1t 10 the une
qual expansion OF the sides OF the Monument IN con
sequence OF unequal exposure to the sun
4 tnef description OF the present condition OF the
Monument viii and IN understanding the mode of OBJ
SerN a!On pursued.
TIE obo>k, thirty feet square al the base, rises,
gradually losSCnme. to a pyramldal summit TWO nun
dred ana lWcnty-One feet. Within is circular well,
seven feet IN diameter at the bottom, and hye at the
top. where II opens into chamber or observatory
The chamber Is approached by winding stairway.
In the center OF the root OF the chamber s an iron
staple which was securely fixed al the time of placing
the Capstone. IL served at first 10 support machinery
for carrying visitors up and down From this staple,
which Is Over The center OF the open space or well.
the pendulum i suspended 10y means OF a screw
clamp.
From point in the floor directly below the index
attached 10 the ball, cces were described and gra-
duaiod, and radn drawn.
On The dav following the graduation, the index
was found to be on one side of the center OF the
circle. As The scTew-Clamp hrst employed did not
ADMIT Of adjustment, a new apparatus, with the ne
cosSSIy notifications, was substituted and the oau
brought precisely over the centre Of the graduated
circle.
few hours later II was found out OF the center
Iron observing more carefully, II was found
during clear DAYS that the motion Of the ball IN the
morning was 10 the westward, al noon 10 the north
west. and al evening TO the east. II was further oo
served that on days when the sun was obScured by
clouds that 10 motion of the ball Oh H. index point
occurred. II was Stlll further observed on one Oc-
CaSlon, during sudden shower. accompanied with
strong wind from The southeast al about three O'Clock
in the afternoon, 10 move IN the space OF very few
minutes a quarter of IN inch To the eastward. 90
scnalons al : IN the morning, al L. NJ and at L. VI
were recorded through several weeks, and no doubt
remains that cause COlncldent Win The sun IN rs
progress produced the variation OF the perpendicular
IN the Monument.
4 fact. already limited al, further conhrmed this
conclusion The extreme departure OF the ball from
the center was 20 the west OF northwest not 10
the north as might al first glance be supposed The
explanation found IN the position OF the Monument
Its eides DO not face the Cardinal points but are in
clned about 9O'. The expansion Of a single SIDE
would produce inclination III direction perpendlcu-
lar 10 the SIDE.
The expansion of two ad accent sides would pro
duce inclination IN the direction oi the diagonal In
the morning the Shaii IS inclined 10 the westward.
Al noon Il 5 inclined but little 10 the north OF west
In the progress OF the afternoon. IL sweeps over