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XVIII. Contributions to Terrestrial Magnetism. — No. VIII. 
By Lieut. -Colonel Edward Sabine, R.A., For. Sec. R.S. 
Received June 15, — Read June 18, 1846. 
Containing a Magnetic Survey of the Southern Hemisphere between the Meridians of 
0° and 125° East, and Parallels of —20° and — 70°. 
THE Antarctic Expedition, under Captain Sir James Clark Ross, R.N., has fur- 
nished the materials for maps of the three magnetic elements in the high latitudes of 
the southern hemisphere for nearly two-thirds of its circumference. The first and 
second portions of the results, comprising between the meridians of 125° and 300°, 
have already been communicated to the Royal Society, and are contained in the Vth 
and Vlth Numbers of these Contributions* ; a third portion, comprehending between 
the meridians of 300° and 360°, is in preparation and will shortly be laid before the 
Society. In order to complete the magnetic survey of the high latitudes of the 
southern hemisphere as far as they are accessible, there remained the portion between 
the longitudes of 0° and 125°, or thereabouts. The tracks of vessels in the employ 
of the enterprising merchants, the Messrs. Enderby, had shown that no difficulties 
of serious importance obstructed the navigation of the ocean in the vicinity of the 
Antarctic Circle between the meridians specified : and there appeared to be little 
reason to doubt, that a vessel, despatched from the Cape of Good Hope, might accom- 
plish this remaining portion of the survey in a single season, without encountering 
any particular risk. 
Lieut. Clerk, of the Royal Artillery, had been attached by Lord Vivian, Master- 
General of the Ordnance, to the Magnetic Observatory at the Cape of Good Hope, 
with the express view of being engaged in a magnetic survey, either of the colony 
itself, or of such portion of the globe as might be conveniently accessible from it ; and 
on his passage from England to the Cape had had an opportunity of practising with 
the instruments employed in a magnetic survey conducted on the ocean. The com- 
pletion of the survey of the high latitudes appeared the most important service which 
Lieut. Clerk could render to magnetical science; and on its being proposed to him, 
he most readily undertook it. 
In June 1844 the subject was brought under the consideration of the Committee of 
Physics of the Royal Society, by a letter from myself to Sir John F. W. Herschel, Bart., 
Chairman of the Committee, accompanied by one addressed by Sir John Herschel 
to the Committee, expressing his earnest hope that the measures suggested for the 
* Philosophical Transactions, 1843, Art. X., and 1844, Art. VII. 
