284 Report of.the Voyage of Discovery 
derably removed from the first of these islands, approaches, on 
the contrary, the second, which it will even reach in a few 
years. The magnetic meridian of the Cape, produced to- 
wards the north, passes at a little distance from one of the 
nodes towards the west: hence the inclination must rapidly 
increase there; and this is what the observations of Cook, of 
Bayly, of King, of Vancouver, and of Freycinet, also show. 
At Otaheite, Bayly, Wales, and Cook found, in 1773, 1774, 
and 1777, a dip of the needle of about 30°; M. Duperrey de- 
duces from his observations 30° 36’; the annual change then 
is nearly insensible: but the magnetic meridian of Otaheite 
also meets the line without dip very near to its maximum of 
latitude; that is to say, in a point where this curve is nearly 
parallel to the terrestrial meridian. ‘The rapid change of dip 
at Conception in Chili, deduced from the comparison of the 
observations of Malaspina and of M. Duperrey; the inconsi- 
derableness, on the contrary, of this motion at the Sandwich 
Islands, which seems to us to result from the observations of 
Bayly, Cook, Vancouver, and M. Freycinet, present a no less 
striking confirmation of the rule. 
If an exact investigation of the observations on the hori- 
zontal needle showed, what at first sight appears to be the 
case, that in each place the changes of variation may also 
be connected with the position of the magnetic equator, the 
study of the motion of this curve would acquire a new import- 
ance. It is an inquiry of which MM. Freycinet and Du- 
perrey possess all the elements, and which appears to us 
worthy of occupying their attention. We shall content our- 
selves here with remarking, that it results from the observa- 
tions of these two officers, compared with those of Cook and 
Vancouver, that the declination, whether at Otaheite, to the 
south of the two equators, or at the Sandwich Islands, in a 
northern latitude, is still as little variable as the dip. 
The maritime expedition of the Uranie is the first during 
which the diurnal oscillations of the horizontal magnetic needle 
were studied. The valuable observations published by M. Frey- 
cinet have established in an incontestible manner, that between 
the tropics the extent of this oscillation is sensibly less than in 
our climates. It would also appear that we may infer that 
in the southern hemisphere, whatever be the direction of the 
dip, the northern extremity of the needle moves towards 
the east at the same hour when we see it in Europe vary to- 
wards the west. This fact, in its turn, led to the consequence, 
that between Europe and the regions where M. Freycinet’s 
observations were made, points must be found in which the varia- 
tion would be absolutely nothing. There remained only to de- 
termine 
