24 . SEVENTH REPORT—1837. 
here to say, that, they traversed the whole of the north of 
Europe and of Asia longitudinally, and descended the rivers 
Oby and Jenesei to the polar circle, with a view of determining 
the latitude and longitude of the Siberian pole or centre 
of magnetic intensity; and that its general phenomena were 
found to correspond in a very remarkable degree with M. 
Hansteen’s anticipations, its locality being removed but a few 
degrees (about 6°) to the eastward of the position he had pre- 
viously assigned to it. 
Soon after M. Hansteen’s return, he published a general 
map of the magnetic intensity, in the xxvilith vol. of the An- 
nalen der Physik. Y am not aware that he has as yet pub- 
lished any detailed statement of the results of his journey. The 
stations inserted in the table in this memoir are from a MS. co 
of his and Lieut. Due’s observations, which, with the liberality 
that has hitherto characterised the labours of those engaged in 
this interesting inquiry, and which I trust may long continue to 
do so, he sent me from Irkutsk in 1829, with permission to make 
“‘ every use of it that I might think proper, especially when it 
can encourage to new undertakings, and accordingly forward 
the science.” 
M. Hansteen’s determinations of intensity have a very great 
advantage in the perfect invariability of the needle he em- 
ployed. For sixteen years in which it was in constant use no 
sensible alteration took place in its magnetism. This is an ad- 
vantage which only those can duly appreciate who have been 
much engaged in making or in computing observations of this 
nature. The correction for temperature also, which he deter- 
mined experimentally in the usual manner, has received the 
fullest practical confirmation, by the exact agreement, when 
corrected by it, of observations at the same place in tempera- 
tures differing nearly 90° of Fahrenheit. 
M. Erman’s intensity observations are not yet published ; 
they are to form a part of the second volume of the scientific 
portion of his journey, the first volume of which was published 
at Berlin in 1835. He has, however, communicated their re- 
sults, provisionally computed, with corrections applied for tem- 
perature and arc, in the xviith vol. of the Annalen der Physik, 
from whence I have extracted them. 
The number of stations entered in the table are, 80 observed 
by MM. Hansteen and Due, and 98 by M. Erman.. These are 
all in the north of Europe and Asia, and 46 are common to 
M. Erman and MM. Hansteen and Due. There are besides 
four land determinations of M. Erman’s on his homeward voy- 
age, viz., Sitka, St. Francisco in California, Otaheite, and Rio 
ee eke ee ee ad er 
Hi 
Ly 
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