i ■ J
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' ii*
I I . Dip.
T h e fo llow in g ta b le e x h ib its th e c om p a riso n o f C ap ta in F it z R
o y ’s o b s ervations o f . th e d ip in th e so u th e rn h em isp h e re , w ith
th o se o f e a rlie r o b se rv e rs, a t statio n s w h e re th e m a te ria ls for su ch
a com p a riso n exist.
Observer.
L a C aU le
C o o k
S a b i n e
D u p e r r e y
F i t z - R o y
A s c e n s i o n .
Date.
1754
1775
1 8 2 2
1 8 2 5
1 8 3 6
Variation.
11, 10 N.
8 . 67 N .
4- 3 0 N .
1 . 5 8 N .
1 . 3 9 N .
S t . H e l e n a .
L a C a i l l e . . 1754 9- ° S .
C o o k . . . . 1 7 7 5 11. 2 5 S .
F i t z - R o y . . . . 1 8 3 6 j 8. 0 1 S .
C a p e o p G o o n H o p e .
L a C a i l l e
B a y l e y . .
B a y l e y . .
A b e r c r o m b i e
B a y l e y
F r e y c i n e t
F i t z - R o y
1751
1 7 7 2
>775
1775
1 7 7 e
1 8 1 8
1 8 3 6
43- o S .
4 5 . 37 S .
45- 1 9 S .
4 6 . 2 6 S .
4 6 . 3 1 S .
5 0 . 4 7 S .
5 2 . 35 S .
B I a u r i t i u s ( P o r t L o u i s ) .
L a C a i l l e . . . . 1754 5 2 . 1 7 S .
D u p e r r e y . . 1 8 2 4 5 3 . 5 1 S .
F i t z - R o y . . 1 8 3 6 5 4 . 0 1 S .
O t a h e i t e .
C o o k . . . . 1 7 7 3 2 9 . 4 3 S .
C o o k . . . . 1 7 7 4 2 9 - 5 9 8 .
B a y l e y . . . . 1777 2 9 . 4 7 S .
D u p e r r e y . . 1 8 2 3 3 0 - 0 3 8 .
E r m a n . . . . 1 B 3 0 3 0 . 2 9 , 5 8 .
F i t z - R o y . . 1 8 3 5 3 0 . 1 3 , 5 s .
L i m a a n d C a l l a o .
F e u i l l e e . . . . 1 7 1 0 1 0 . 3 0 S .
H u m b o l d t . . 1799 9. 59 8 .
D u p e r r e y . . 1 8 2 3 8 . 3 3 S .
F i t z - R o y . . . . 1 8 3 5 7 . 0 3 S .
V a l p a r a i s o .
M a l a s p i n a . . 1793 44- 58 S .
V a n c o u v e r . . 1795 44- 15 8 .
L u t k e . . . . 1 8 2 7 3 9 . 5 6 S .
K i n g . . . . 1 8 2 9 4 0 . 1 1 S .
F i t z - R o y . . . . 1 8 3 5 3 8 . 0 3 S .
C 0 N C E P 9 1 0 N .
F e u i l l e e . . . . 1 7 1 0 55. 3 0 S .
P e r o u s e . . . . 1 7 8 6 5 0 . 0 0 S .
Obse rve r. Date. Variation.
L ü t k e . . . . 1 8 2 7 4.5. 3 3 S .
K i n g . . . . 1 8 2 9 4 5 . 1 0 S .
F i t z - R o y . . . . 1 8 3 5 4 3 . 1 5 S .
K i n g G e o r g e S o u n d .
V a n c o u v e r . . 1 7 9 I 6 4 - 54 8 ,
F l i n d e r s . . . . 1 8 0 1 6 4 . 0 1 S .
F i t z - R o y . . . . 1 8 3 6 6 4 . 4 1 S .
V a n D i e m e n ’s L a n d .
C o o k . . . . 1 7 7 7 7 0 . 1 5 8 .
B e r t r a n d . . . . 1 7 9 2 7 0 . 5 0 S .
D e n t r e c a s t e a u x 1 7 9 2 7 0 . 3 0 S .
D e R o s s e l . . i 793 7o . 1 0 S .
F i t z - R o y . . . . 1 8 3 6 7 0 . 3 5 S .
S y d n e y .
F l i n d e r s . . . . 1 8 0 3 6 2 . 5 2 S .
F r e y c i n e t . . 1 8 1 9 6 2 . 4 7 S .
B r i s b a n e . . . . 1 8 2 1 6 2 . 3 6 S .
D u p e r r e y . . 1 8 2 4 6 2 . 2 0 S .
F i t z - R o y . . . . 1 8 3 6 6 2 . 4 9 S .
N . Z e a l A N D ( B a t O F I s l a n d s ) .
D u p e r r e y . . . . 1 8 2 4 5 9 . 4 5 S .
F i t z - R o y . . . . 1 8 3 5 5 9 . 3 2 S .
T i e r r a D E L F u e g o .
B a y l e y . . - . I
L a t . 5 5 ° . 2 2 ' ; > 1 7 7 4 6 5 ,6 4 8 .
L o n g . 7 0 . 0 3 . J
K i n g . . . . )
L a t . 55° - 5 1 ' ; f > 8 2 8 5 9 . 4 4 S .
L o n g . 6 7 . 3 4 . 3
F a l k l a n d I s l a n d s .
F r e y c i n e t . . . . 1 8 2 0 5 5 . 2 0 S .
D u p e r r e y . . 1 8 2 2 5 4 . 4 9 S .
F i t z - R o y . . . . 1 8 3 3 - 4 5 3 . 2 5 S .
S t a C a t h a r i n a .
D u p e r r e y . . 1 8 2 2 2 2 . 5 4 S .
K i n g . . . . 1 8 2 7 2 2 . 1 2 S .
R io d e J a n e i r o .
L a C a i l l e . . . . 1 7 5 1 2 0 . o S .
F r e y c i n e t . . 1 8 1 7 1 4 . 4 2 S .
K i n g . . 1 8 2 6 1 4 . 0 0 S .
L ü t k e . . . . 1 8 2 7 1 4 . 3 5 S .
E r m a n . . . . 1 8 3 0 1 3 . 3 1 S .
F i t z - R o y D u p e r r e y . . 1 8 2 3 4 4 . 5 5 S . . . . . 1 8 3 2 1 3 . 3 7 S .
W e m ay classify th e ch an g e s w h ich a re ta k in g pla c e in th e d ip
in th e so u th e rn h em isp h e re in fo u r divisions, c h a ra c te ris e d b y an
a lte rn a te in c re a se a n d d e c re a s e o f d ip . C om m en c in g w ith th e
m e rid ia n o f G re e nw ich , a n d p ro c e ed in g e a s tw a rd ly ro u n d th e
h em isp h e re , we m a y d is tin g u is h th e divisions as follows, in th e
o rd e r o f th e ir g e o g ra p h ic a l succession.
Hi . South dip increasing.
annually.
S t . H e l e n a . . . . 1 7 5 4 t o 1775- - 6 , 9 '
D o ...............................1 7 7 5 1 0 1 8 3 6 . - 6 , 5
C a p e o t G o o d H o p e 1 7 5 1 t o 1 7 7 5 . - 7 , 2
annually.
C a p e o f G o o d H o p e 1775 t o 1 8 3 6 . . 6 ,6 .
M a u r i t i u s . . . . 1 7 5 4 1 0 1 8 2 4 . - 1 , 3
D o ................................. 1 8 2 4 1 0 1 8 3 6 . - 0 , 8
T o th is d iv isio n also b e lo n g s A sc en sio n ; b u t as th e n o r th e n d o f
th e n e ed le d ip s a t th a t is lan d , th e ch a n g e is north dip diminishing,
in s te a d o f south dip increasing.
A s c e n s i o n ............................. 1754 t o 1 7 7 5
D o . ............................. 1 7 7 5 1 0 1 8 3 6
6 , 3 a n n u a l l y .
7,2 ---------
N e w Z e a l a n d
O t a h e i t e
L im a a n d C a l l a o .
D o . . . .
V a l p a r a i s o . .
C o n c e p ç i o n . . .
D o . . . .
2d. South dip decreasing.
1 8 2 4 1 0 1 8 3 5 . . 1 ,2 a n n u a l l y . *
3d. South dip increasing.
. . . . . . 1 7 7 5 t o 1 8 3 6 . . 0 , 5 a n n u a l l y .
Lth. South dip decreasing.
annually.
1 7 1 0 t o 1 7 9 9 . - 0 , 4 '
1 7 9 9 t o 1 8 3 5 . - 4 , 9
1 7 9 4 1 0 1 8 3 5 1 0 , 0
1 7 1 0 1 0 1 7 8 6 . - 3 , 7
1 7 8 6 1 0 1 8 3 5 . - 8 , 3
T i e r r a d e l F u e g o
F a l k l a n d I s l a n d s
S t i C a t h a r i n a . .
R i o d e J a n e i r o . -
D o ............................
annually.
1 7 7 4 t o 1 8 2 8 . . 8 ,0
1 8 2 0 t o 1 8 3 4 . - 8 , 2
1 8 2 2 t o 1 8 2 7 . - 8 , 4
1 7 5 1 t o 1 8 1 7 . . 4 , 8
1 8 1 7 t o 1 8 3 2 . . 4 , 3
In th e 2 d a n d 3 d div isio n s th e a n n u a l ch a n g e is sm all ; in th e
1 st a n d 4)th c o n sid e rab ly g re a te r. I t is g re a te s t a t th e so u th e rn
sta tio n in S o u th A m e ric a ; th e o b serv atio n s a t V a lp araiso , C o n -
c ep 9ion, T ie rra d e l F u e g o ; a n d th e F a lk la n d Is lan d s, co n cu r in
sh ew in g it to ex ceed 8'. T h e o b s e rv a tio n s a t Ascension, S t. H e len a ,
a n d th e C ap e o f Good H o p e , c o n cu r in s h ew in g a n a n n u a l c h an g e
in th a t q u a rte r o f th e 1 st d iv is io n e x c e e d in g 6 '.
A s th e so u th d ip decreases in S o u th Am e ric a , a n d in c re a se s in
A frica, i t is obvious th a t som ew h e re in te rm e d ia te ly th e d ip m u s t
b e s ta tio n a ry . B e tw e e n A frica a n d N ew Z e a la n d , fo r th e same
re a son, th e r e m u s t b e a s econd lo c a lity so ch a ra c te ris e d . B etw e en
N ew Z e a la n d a n d O ta h e ite , a th ir d ; a n d b e tw e e n O ta h e ite a n d th e
w e st coast o f S o u th Am e ric a , a fo u r th . C a p ta in F it z -R o y has
• T h i s i s d e r i v e d f r o m t h e o b s e r v a t i o n s o f C a p t a i n s D u p e r r e y a n d F i t z - R o y
a t t h e B a y o f I s l a n d s , i n L a t . 3 5 ° . 1 6 '. T h e i n t e r v a l i s s h o r t ; b u t t h e i n d i c a t i o n
r e c e i v e s c o n f i rm a t i o n f r o m t h e o b s e r v a t i o n s o f C a p t a i n s C o o k a n d V a n c o u v e r a t
D u s k y B a y , N e w Z e a l a n d , i n L a t . 45° - 47'-
C o o k . . . . 1 7 7 3 . . 7 0 ° . 0 6 '
V a n c o u v e r . . 1 7 9 1 . . 6 9 . 4 3
i ' - 4 a n n u a l d e c r e a s e .
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