Latitude S i J . . Judngjtiade W» / Vanatabn.^.Jj'j. | Years;
sh 8.° 48' > , 29®' 37' - v- *■&, 'X ' 177(5 1 1
-- 1 - ' $• m m m t*&*s** iq. -
■■ Praia i L,i. J®.. 1 29 S! H -«■ 54
• ■■ S-h!j BtQtf’jb -’'-St? 40
-lS.r 0 ./• MM|ul <£0
t ( Variation ' fe!
: 6* 45 1 -■ ■ g s.'
. 7 - Variation .W. . ’■
l ■ 5 - f i ’M i 1- lcS4* - 2,0 - | M m i 7
43 - 34- 20 > 1 j
* Variation
1 ' T 4- ' $ * ^ j ^ w ‘"i44
'Vanatibni W1. *:;
j to°,. 4' 34-- ^ 9 — , - il5y<°*ar. ia.t ioil.E..6y.i
12. 4® 34-' 49 -r ■ 12 j: ! *3 ,34- 49 : I. 1'
I: »4-, 11 , •. .34-' 49 I ''’asr*' B 19 I *5- h 34* 4° -- n m m a U B B R
i 16. 12 ■ M - S 20- . t . 4 i
i? S 3S-- |o V;: ■ . 3" 2 '
4 '' no. ' ]8 ' ^ Jjft- I j . 16 q,
-j 2t -_ 37 HB i n s- H n
H B |47 m . j <* |8 (v. -4-3* . *4 8
4r ■ .■ 34- w 37 0 .{..3.- -44 i
2». 4R 1 3*r 40 d | .is t .- ]8 .j
•i 3°- | . Z& -sfS i 7 ' h
li^riati'onlW. 4
I 33- 43 16. - i ° 6 1 .y<4 - 4* i
J 35- S7 M- o t i .JtS- 5 t ■ h
j 38. . y2 1
2S0 .
tude E. 'v|
1 ' M ■ 1 hong:
;■>'-3 2 ..' ■
Vecatiou E.*'^
40- 3« . %i J33r ' 34 H m-' 47 y
•< 4*. . 4 3 1 3Z ■ c 1 j& f , |
Varijation pVjk | •if 44* 5? It t^ i- 47 ■ .-9 . 28 . I
■ | 4& ^ ' I 5 ° 4 *4- 4 8 1
r 4 8 . 4;i 1 &■ | ISO . - a i t 39. >i
Variation obfwotd at -Londpn at deferent
Times'. -. '
Years.
I B B ' K ^ S 11
xi ri
“tU’6-l2-i -.£>• not
1622, , ’ j, f r a g
tf>33 H i f 1
*634 4- t 1
if>51 ;j .O', ir r
1665 1- 2211
1 r:666 . B SEfll
3 ‘Tj>72 • Itji2- isiiy,
I683 ■ 4 ! f |» | | ' L‘iiS^’I'd
■ijrJJ&Si;
17 >7 |
• 1-724 ” • 47
1 *7^5 *1^: s \ i f-Wel!.
| 13 ' 1 4 . 16
- l'D??x;Kb - '- r e .
m m l ’rS-. 5ijt.
■ f '¥ 4
17601, p * SL 'f2 ,
1769' t ‘.Sr
■ TW,^*
S |£ /14>. limit *
2 1~" S‘J -1
, 45 5 \ The pr'gfeijt vacation ,
an$ |On&Feafirfg. JThe .change 13T jvarffltiou isirot | fuf-
ficiendy regular, To; as. to be able Ip ascertain at anyffa-
AjjffiKBnE what the (vacation wlU.ber;
2S5-.'The magnet isi|ubk^t to a daily variation, -which
is affected by heat and cold, as appears by the following
obfervations, made (hy l$^£Ui!j§p|£ge)i
0 } e V a t i ia t i^ ^ f i^ ^ a t - 4 i^ r e n tM Q u n s o f M e
fame B a y, Ju ly 27, . y
1 BMpSEi »iSouri i Min.' •Variation W. Thermo.
it "ots.’;.'' Sfi".-P ' 4^:Ui^tyvy
h 6 . 1 4 -.18. ■‘■'38 '
* 18: •
; 0*84-
Morning i ! 1 2
8KSH
n n ? *
HV i id.'-* .2 ° M
kj! n . fqo ■! ■ *?•' ,..14.6'» r«8S>,
"■yes r |1 *' ;38 "»4&- |'H®f4 ln »vj-.-t
Afternoon i1 I B B •V-‘I'9‘ - '8 -J‘ -68' *
1 7- ■ '20- ■ S 9Vi'4j ^61 Wi-XH1b- ’ 11. f! £■■ '•B B ifi5S«; ':P« '3397i '
mean Variationifof each Month in the
■ Tear.
-'.4ann®ry. ■. . - -- - ■ — i’t V 7'ff
.f^jr-uary ,1., - . i, r 58 ijf
March 17. ;
Ml J 12. 4 ,®ay- '’’- h1’ ,''’?
Jjuue -v . 1 f i 1.j jih. H r H i j l a
*4 , I
K8yjgiij£> . yf ••- ,-j t? - 12. 19,
^September f l'. - - i B | W j '43
)j|ayjpb{< 3^ | |
H 6OT»er;.'.,fir4'. | a | | S f . 9 l]
1 mS H I 6. H ;
B y "this ’tablfe.^t, .appears, that the variation of the
rfeedle'SJgreatlffrnjftmmef, an3(kaft in winter.
4.{ z c v ^ p r . H a l le y nrffc' piiDlyhed ‘ fome variation
charts, from obfervations made at the beginning o f the
^relfcitl^nCilryfi 'Another chart was afterwards fortned
by Mountaine and D odson, upon obfervations made
in 1756. Thefe charts are'thusi comlrilfted. On a
general map o f the world, mark down with dots, all the
then draw
a line through a ll thefe points: thus, marl* down’ with
dots,ilh W i r iw t^ f f c f o a i t jp g ea|t variaijfenj and thaw"
a line through Sail thefe dots; and you get the line o f 2d0
eaft variation. I Wh^Jg the', dots ate a t a confiderdble
distance,fWu mull ■ fell the/fgade ’. 1m tvi^h - a line which
feems moil to accord w ith the tendency o f the line oh
eaclviicfer' T hD r . H a l l o y'k’cKaff, the line off no variation
'Qtdlht-S the^tn^f|l^ui:T)f a trabout the 5 >°
o f fouth latitude; it then proceeds iiiri^iatiihcd manner
towards the-, weft o f the faid meridian, and 'increafifigits
: ^rvature/ds i t hdvantKSLihfoL the.'nOtth^n hdmtfphere,
-termidateiat Sharks iTemih ih /ffsrtiijtmeitea. ■ Ih the
Indian feii^ihetlihes' o f variation areo^ryurre^ulhr.* >
2J&. Themethod’ o f fitidinghy the compafs, the dire
ftion in whichtadhip frofei is t hi 8 the noth pafs is flif-
pended in the cabiili andyotrr look horizontally over th e
cflmpafe'tnfifhewdire&ion of<tfh&'(Blip’ s wake, by which
; yoiiffee the point"!of thfe compafs denoting-the dire61 ion
o fih e wake, the 0pp©ilte*'.p<jm^4o which, is the point to
which you are failing,' according to the eompafs ; and
kilo winghow'ntu elf the compafs varies, y oilcan tell the
true point? o f the honzOn to which y&U are'gOh^l . >. 1
a 59. I f a magnet be fufpended by an horizontal axis,
fo that it’ ctfn freely move in, a vertical plane, it will not
Hand in Sfl horizontal petition, although 'the’ two etiHs
1 OfjStd mhgnet,
: jn-this «art o f the’ tVotld, ■ will- incline towards tbe'hori-
zbn, or dip, as<it (s called, and Of cdurfe the fouth pette
will-be elevated. A n inllrument thus con(lru6led -is
-called 'a dipping needle. A « yoa'„agproach the foutherii
parts o f the earth, the'dip will dfininilh, and at length
the magnet will become horizontal}, and proceeding
y more