406 
MR. CHRISTIE ON THE MAGNETICAL OBSERVATIONS 
of comparison were necessary. At New York the times of vibration were only de- 
termined with the face of the needle to the face of the instrument ; and I have there- 
fore compared these observations with those in London, where the needle was vibrated 
in the same position. At the other stations the observations were made with the face 
of the needle to the face of the instrument, and likewise reversed ; and these obser- 
vations are compared with the similar observations in London. 
Place of observation. 
Date. 
Time of 
vibration of 
needle. 
Thermo- 
meter. 
Measure of in- 
tensity at 
temp. 60°. 
Ratio of in- 
tensity to lhat 
at London. 
London 
1333. 
February 9 , 
s 
1-3625 
50-0 
•5362407 
1-00000 
New York 
April 1 . 
1-28572 
69-0 
•6074147 
1-13273 
London 
February 9» 
1-3828 
50-0 
•5206021 
1-00000 
Fort Alexander 
June 10 . 
1-25315 
71-4 
•6400997 
1-22954 
Cumberland House . 
July 6 . 
1-26505 
62-75 
•6256439 
1-20177 
Isle a la Crosse 
July 17. 
1-2750 
74-25 
•6191539 
1-18930 
Fort Chipewyan . . . 
July 31. 
1-2715 
95-0 
•6283987 
1-20706 
Fort Resolution 
August 9* 
1-2500 
64-8 
•6413976 
1-23203 
October 9- 
1-27455 
41-9 
•6105560 
M7279 
Fort Reliance ^ 
1834. 
May 21. 
1-2772 
49-63 
•6101570 
1-17202 
October 9* 
1-27567 
29-81 
•6061936 
1-16441 
- 
Mean . . 
•6089689 
1-16974 
From these results it is very evident, that, from some cause or other, very possibly from 
having- been subjected to a hig-h temperature, the magnetism of the needle suffered a 
permanent change in the interval between the observations at Fort Resolution on the 
9th of August, and those at Fort Reliance on the 9th of October. Judging from the 
results of the observations at Fort Reliance in May 1834, and those in October of the 
same year, it would not appear that the magnetism of the needle underwent any ma- 
terial change during that interval ; for although the intensity, as deduced in this 
Table, is somewhat less in October than in May, yet, as will be seen in the Table 
which I shall immediately give, taking the vibration with the face of the needle to 
the face of the instrument alone, the intensity appears to be rather greater in October 
than in May. Whether the magnetism of the needle stiff red any change in the in- 
terval between the observations in London and those at Fort Resolution, cannot be 
determined ; but it is at least not probable that it did so from New York, and the 
result at that city would not lead us to suppose that it had previously. We may 
therefore consider that no exception can be taken to these results on this ground. 
With regard to the results at Fort Reliance, the observations that were made in 
London, subsequent to the expedition, indicate that they are considerably in defect, 
as will be seen by the comparison which I shall now make between the observations 
at Fort Reliance and those at stations subsequently visited. 
In tbe observations which were made in the course of Captain Back’s perilous 
voyage to the mouth of the Thlew-ee-choh, — which river, in justice to its discoverer 
