150 
MAJOR SABINE ON TERRESTRIAL MAGNETISM. 
fort’s permission, from Captain Wickham’s Report in the Hydrographic Office. The 
experiments to determine the effect of differences of temperature on the times of 
vibration do not appear to have been yet made, and are probably deferred until 
Captain Wickham’s return to England at the conclusion of the service on which he 
is still employed. The provisional results which are here computed are therefore ne- 
cessarily uncorrected for temperature. 
Station. 
Date. 
Needle Y. 
Needle Z. 
Dip. 
Time. 
Therm. 
Time. 
Therm. 
Plymouth 
June 26, 1837- 
s 
806*5 
O 
71 
s 
883*3 
O 
72 
O / 
69 12 
Santa Cruz 
July 21, 1837. 
691-7 
87 
750-6 
88 
57 48 
Bahia 
Aug. 31, 1837- 
610-9 
86 
660 5 
88 
5 35 
Cape of Good Hope . . 
Sept. 27, 1837- 
725-3 
65 
781-9 
73 
— 52 53 
Swan River 
Nov. 22, 1837- 
655-1 
79 
702-4 
79 
— 62 23 
Point Swan 
Feb. 5, 1838. 
578-9 
93 
632-9 
93 
— 43 07 
Port Usborne . 
March 24, 1 838. 
584-1 
99 
627*2 
99 
— 43 26 
Port George IV 
April 15, 1838. 
577-6 
94 
619-6 
93 
-41 29 
Swan River 
June 15, 1838. 
662-7 
64 
710-8 
63 
-62 25 
Hobart Town 
July 16, 1838. 
742-2 
54 
795-7 
54 
-70 25 
Sydney 
Oct. 25, 1838. 
661-2 
71 
709-1 
71 
— 62 53 
Three Hummock Island 
Dec. 11, 1838. 
724-7 
70 
778-3 
69 
-69 08 
Dunheved 
March 22, 1839- 
664-1 
78 
712-4 
80 
— 62 45 
Paramatta 
April 4,1839. 
660-9 
67 
708-4 
67 
-62 50 
Sydney 
April 16, 1839- 
661-8 
70 
709-9 
69 
-62 50 
The observations of this series furnish tests of the steadiness of the magnetic con- 
dition of the needles, or of the changes undergone by them in this respect, during two 
intervals, viz. from the 22nd of November 1837 to the 15th of June 1838, at both 
which dates they were vibrated at Swan River; and from the 25th of October 1838 
to the 16th of April 1839, at both which dates they were vibrated at Sydney. In the 
second interval neither needle appears to have sustained any change deserving of 
notice ; the times of vibration in October 1838 and in April 1839 differing only within 
the limits of the known fluctuations of the horizontal force at the same station on 
different days, and even on the same day. Between the observations at Swan River 
in November 1837 and June 1838, both needles appear to have lost force, equivalent 
in the case of Y to 7 S, 6 in 662 s, 7, and in that of Z to 8 S, 4 in 710 S, 8. During the re- 
maining portions of the series, viz. from June 26, 1837, to November 22, 1837, and 
from June 15, 1838, to October 25, 1838, the observations furnish no direct or inde- 
pendent means of testing the needles ; but an attentive consideration of their times 
of vibration leads to the inference, that Y must have lost magnetism considerably 
between June and November 1837, and that the loss took place in all probability in 
the early period of the voyage, or between Plymouth and Santa Cruz ; whilst in the 
case of Z, there is no indication of any other loss than that shown to have taken place 
by the observations at Swan River. Admitting and allowing for that loss, and sup- 
posing no other to have taken place, the values of the intensity given by this needle, 
