LINES OF MAGNETIC DECLINATION IN THE ATLANTIC. 
191 
From these we obtain A=+8'; D=-{~14'; E= — 2'; B at Nassau =4-‘062, and 
at Gillingham +*111 ; C at Nassau = — *006, and at Gillingham = — -007. 
From Nassau the Thunder passed immediately into dips on the coast of America 
higher than those in the subsequent portion of her voyage, or than the dip at Gil- 
lingham. The variable part of the disturbance therefore, probably, increased rapidly 
after leaving Nassau, and may have been greater whilst the ship was off the coast of 
America than when examined at the termination of the voyage. Having no inter- 
mediate data, however, I have not ventured to exceed the maximum observed value 
of v^B^-l-C^, but have commenced with -l-‘062, the observed value at Nassau on the 
1st of May, and increased it uniformly with the time to -f-Tll, the observed value 
at Gillingham, and have supposed it to have attained the latter value on or about 
the 1st of June, when the ship had been a fortnight in dips exceeding that in the 
Thames. 
Determinations in the Prince Regent Transport, on the passage from England to Canada 
in 1842, hy Lieutenant {since Captain) J. H. Lefroy, R.A. 
These observations were made by Lieut. Lefroy when proceeding to Canada in 
1842 to take charge of the Magnetic Observatory at Toronto. By direction of the 
Hydrographer, Lieut. Lefroy was furnished with one of the Admiralty compasses, 
which was fixed as a standard in the usual manner. The Prince Regent was swung 
at Greenhithe by Captain Johnson, R.N., from whom I received the following table 
of deviations. 
Table IV. — Disturbance of the Compass in the Prince Regent Transport. 
Ship’s head. 
Disturbance 
towards the 
west. 
Ship’s head. 
Disturbance 
towards the 
west. 
Ship’s head. 
Disturbance 
towards the 
west. 
Ship’s head. 
Disturbance 
towards the 
west. 
o / 
o / 
O / 
N. by w. 
+ 0 45 
w. by s. 
+ 2 40 
s. by E. 
+ 0 05 
E. by N. 
— 2 00 
N.N.W. 
+ 1 55 
w.s.w. 
+ 2 20 
S.S.E. 
— 0 10 
E.N.E. 
— 1 45 
N.w. by N. 
+ 2 05 
s.w. by w. 
+ 2 05 
s.E. by s. 
-0 35 
N.E. by E. 
— 1 35 
N.W. 
+ 2 15 
s.w. 
+ 2 00 
S.E. 
— 0 35 
N.E. 
— 1 05 
N.W. by, w. 
+ 2 15 
s.w. by s. 
+ 1 35 
s.E. by E. 
-1 05 
N.E. by N. 
— 0 25 
W.N.W. 
+ 2 25 
s.s.w. 
+ 1 15 
E.S.E. 
— 2 00 
N.N.E. 
-0 15 
w. by N. 
+ 2 30 
s. by w. 
+ 1 05 
E. by s. 
-2 05 
N. by E. 
-0 10 
w. 
+ 2 25 
s. 
+ 0 25 
E. 
-2 05 
N. 
+ 0 05 
From this table we have the following values of the coefficients; — 
rA+27 
Permanent coefficients <^D-1- 5 
Ie “{- 10 
Variable coefficients 
fB-f--0389 
lc--oooi 
was read, had a motion of adjustment to suit different eyes. An adjustment of this nature was found liable to 
introduce errors, and has since been discontinued. The prisms are now fixed, immoveably, at a distance from 
the card adapted for eyes of ordinary vision. 
2 c 2 
