LIEUT.-COLONEL SABINE ON TERRESTRIAL MAGNETISM. 
171 
General Remarks . — The Tables of the declination observations in the Erebus and 
Terror, and of the inclination and intensity observations in the Erebus, furnish a 
full opportunity, for those who may desire it, to examine how far the corrections 
computed in the manner which has been described fulfil their purpose. 
The three charts which accompany this number of the “ Contributions,” exhibit to 
the eye the determinations contained in the Tables, arranged in their respective loca- 
lities, by which their general harmony may be, in some measure, judged of. The 
faint lines, representing the principal curves of the magnetic elements, are drawn in 
approximate conformity with the observations, and are designed merely to assist the 
eye in taking a first general view of the results. When the determinations of the 
succeeding voyages shall have been laid down in a similar manner on a south polar 
chart, they will furnish the means of judging of the course of the magnetic curves 
more comprehensively and accurately, and of tracing them accordingly. 
Rather more attention has been bestowed on the lines in the chart of the inclina- 
tion than in the other two charts, because it has been used for the values of & in the 
declination-corrections. Having had experience in drawing similar charts on former 
occasions, and particularly those of the Magnetic Survey of the British Islands, I have 
no hesitation in recognising with Captain Ross, that as great, and greater, discrepan- 
cies are to be looked for, and must frequently be experienced, in magnetic surveys 
conducted on land, than in those made at sea. The chart of the inclination which 
accompanies this paper, constructed from observations made at sea, and certainly not 
under the most favourable circumstances, except in the skill of the observers, exhibits 
by no means a greater measure of discrepancy than the magnetic chart of Scotland 
or of Ireland: and it may be further noticed, that the only results which have been 
excluded altogether from the chart, by reason of their excessive discordance as well 
with each other as with the general body of results, are some that were made on 
islands which presented themselves in the course of the voyage. 
I cannot close this section without calling the attention of all who take interest in 
the results of these researches, to the invaluable aid for which magnetical science is 
indebted to Mr. Fox. Without his instrument and method, which render observa- 
tions of inclination and intensity made at sea nearly or altogether equal to those 
which could be made on land or on ice, such were the difficulties of the navigation, 
and such the inaccessible though magnificent character of the coast that was disco- 
vered, that two of the three charts herewith presented, and especially that of the in- 
tensity, must have offered an appearance very different from that which they now 
exhibit. 
To enter into a lengthened comparison of the results now communicated with 
those of preceding observers, which have been embodied in magnetic maps con- 
structed either directly from the phenomena, or by means of the mathematical theory 
of M. Gauss, would be to anticipate the more proper opportunity which will present 
itself, when the whole of the materials collected by the Antarctic Expedition shall be 
2 A 
MDCCCXLIII. 
