54 REPORT—1843. 
Report of the Committee, consisting of Sir Jonn Herscuen, the 
Masrer or Trinity Coutuece, Cambridge, the Dean or Exy, 
Dr. Luoyp, and Colonel SABINE, appointed to conduct the co-ope- 
ration of the British Association in the system of Simultaneous 
Magnetical and Meteorological Observations. 
In this their Fifth Report on the momentous subject entrusted to them, your 
Committee propose to follow the arrangement of the matter under the several 
heads adopted in their report of last year, and in nearly the same order, as 
on the whole most convenient and perspicuous. 
1. Antarctic Expedition. 
The Committee congratulate the Association on the approaching return of 
this expedition, having accomplished in the fullest degree all the objects of 
its mission. Three seasons in which they have forced their way at different 
points far within the higher latitudes of the southern hemisphere, have fur- 
nished a magnetic survey of these regions equalling, or rather surpassing, 
both in completeness and accuracy, all those sanguine expectations which led 
the Association to urge on the Government the prosecution of this great en- 
terprise. Though not marked by geographical discoveries of equal splendour 
with those which signalised their first campaign in the Antartic Circle, and 
which we had the gratification of noticing in our last report, the two suc- 
ceeding seasons have each produced an equally rich harvest of magnetic 
results. 
The observations as they have reached England have been committed for 
publication (as noticed in our last report) to the superintendence of Colonel 
Sabine, and under the form and in continuation of a series of “‘ Contributions 
to Terrestrial Magnetism,” are in process of communication by him to the 
Royal Society, and of publication by that learned body in their Transactions. 
In our last report we gave some account of a communication of this descrip- 
tion, in which the observations made between England and Kerguelen’s 
Island are published and discussed. The 5th of these series (which is now 
in progress of printing) contains, comprised in about sixty pages of tables, 
the observations within the Antarctic Circle, made in the summer of 1840-41, 
on board of both the ships, as also those on board of the Erebus, between 
Kerguelen’s Island and Van Diemen’s Land. In this paper the important 
subject of the corrections due to the iron of the ships is fully considered, 
and by the aid of formule furnished by Mr. Archibald Smith of Trinity 
College, Cambridge, and founded on the theory of M. Poisson, delivered in 
his Memoir of 1838, “ Sur les déviations de la Boussole produites par le fer 
des Vaisseaux,” the constant coefficients of these corrections for each ship 
are investigated. These coefficients are four in number for each ship, falling 
naturally into two pairs, the one depending on a series of compass azimuths 
observed and compared with the true azimuths round a whole revolution of 
the ship’s head at a fixed station ; the other on a series of inclinations or dips 
observed in the same situations of the ship, and compared inéer se. Obser- 
vations for this express and most important purpose were made (in confor- 
mity with the general instructions) at several stations, viz. at Chatham, be- 
fore the departure of the expedition, at Hobart Town (Van Diemen’s Land), 
and at Auckland Island. From these Colonel Sabine has obtained three sets 
of values of the former pair, and two of the latter, and the results thus pro- 
cured (by no trifling amount of calculation) are found to agree admirably ; 
thus affording ground for the fullest confidence in the corrections depending 
on them, as well as in the theory from which they are derived, and in the general 
bet. Detach .- i ow 
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