ON MAGNETICAL AND METEOROLOGICAL OBSERVATIONS. 55 
approximation to truth of the hypotheses necessarily made as to the distribu 
tion of the iron in the vessels. In the case of one of these coefficients an 
opportunity was afforded of testing its value by a series of observations made 
in a high south latitude, by employing a different formula involving the true 
dip, as actually observed on the ice at the moment; and the result proved in 
perfect accordance with the mean of those deduced by the other method. 
There is one other constant, which affects the intensity, entering as a general 
multiplier for the reduction of the observed to the true intensity. The value 
of this for the Erebus is obtained by Colonel Sabine from a series of obser- 
vations made at Hobart Town with Mr. Fox’s intensity apparatus, similarly 
instituted throughout a complete revolution of the ship’s head; the partial 
results of which, grouped by pairs, and checked by the use of observed in 
place of computed values of the disturbed inclination, offer an agreement 
highly satisfactory. 
The above statement applies to the Erebus. For the Terror the first pair 
only of constants (those depending on the azimuths) are deduced; from 
observations at Chatham and Hobart Town, the constants for correction of the 
dip and intensity could not be obtained, the requisite observations not 
having yet reached England. 
Besides these there are a variety of index corrections and other elements 
for the observations of inclination and intensity, which having been com- 
puted and duly applied, the tabulated results have been projected by Colonel 
Sabine in three charts (copies of which accompany this report), exhibiting 
both the individual results, and the approximate course of the isogonic 
and isoclinal lines deduced from them, an inspection of which gives room for 
several interesting remarks. 
1. As great and greater discordances are to be looked for, and must fre- 
quently be experienced in magnetic surveys conducted on land, than in those 
at sea. In effect, the chief and worst cases of discordance occur in observa- 
tions made on the islands at which the expedition touched. 
2. The general form of the curves of higher inclination in the southern 
hemisphere is much more analogous to that in the northern than appears in 
M. Gauss’s maps. 
8. Captain Ross’s observations of intensity lead also to the conclusion of 
a much closer analogy between the two hemispheres than M. Gauss’s maps 
would appear to indicate. No higher intensity than 2:1 has been any where 
observed. 
4. In examining the observations of declination, particularly those which 
point out the course of the lines of 0° and 10° east, a more westerly position 
is indicated than that assigned by M. Gauss for the spot in which all the 
lines of declination unite. 
It cannot be indifferent to the British Association to learn, that first, by 
the blessing of Providence, and next by the watchful care and the expe-~ 
rienced judgment of the Commander of the Expedition, all those results have 
been obtained without any of those drawbacks to which, from the duration 
and peculiar hazards of the voyage, it might perhaps have been deemed un- 
usually liable. Captain Ross closes his last dispatch to the Admiralty, dated 
from the Cape of Good Hope in April 1843, with the following remarkable 
sentence :—“ It affords me the highest gratification for a third time, to report 
that our ships have sustained no material damage ; that we have not been 
visited by casualty or sickness, and that there is not an individual in either 
ship in the Sick Report.” 
