jg SEVENTH REPORT—1837. 
the first voyage that it was not used in the second. Another, 
No. 1, appears to have been subject to fluctuations in its 
magnetic condition, rather than to have undergone permanent 
or uniform gain or loss. M. Hansteen, who has discussed 
these observations at some length in the ixth volume of 
the Annalen der Physik, has rejected the results with these 
two needles whenever they differed considerably from those 
of the other four; but has retained and allowed weight 
in the general mean to such of their results as appeared 
to agree with the other needles. Nos. 3, 4, 5, and 6 showed 
.on their return to England small and comparatively unim- 
portant differences from their times of vibration previous to 
their departure. M. Hansteen has applied corrections on this 
account to the intervening observations, according to their 
dates. One of my stations having been Drontheim in Norway, 
which was visited by M. Hansteen himself for the same purpose 
in 1825, two years after I had been there, it became a station 
common to our respective series ; and he was thereby enabled 
to compute the values of the intensity at all the stations visited 
by me, relatively to the force at Drontheim, which he had 
already compared with Paris by observations at Drontheim 
and Christiania, and at Christiania and Paris. The values so 
computed and published by M. Hansteen in the volume of the 
Ann, der Physik referred to, are here subjoined, for the pur- 
pose of exhibiting them in comparison with my own deduc- 
tions. The latter are made from the observations with Nos. 3, 
4, 5, and 6 alone, those of Nos. 1 and 2 being put wholly 
aside. The times of vibration of each needle at the different 
stations, as originally published in 1825, have received three 
corrections: one, when necessary, for change of magnetism, 
assigned on the principle of uniform gain or loss; a second, 
to diminish the observed times of vibration to the correspond- 
ing times in infinitely small arcs; and a third for reduction to 
a standard temperature of the needle, the coefficients for 
the formula having been determined experimentally for each 
needle. The values of the intensity in my deductions are given 
relatively to the force in Paris, by my own comparison of the 
force in London and in Paris, which will be noticed hereafter. 
There are, therefore, several particulars in which M. Han- 
steen’s mode of deduction and mine differ; but it is interesting 
to perceive how nearly the results agree. The values calculated 
by M. Hansteen are almost everywhere slightly in defect of those 
computed by me. ‘This arises from the force at Drontheim be- 
ing somewhat less by M. Hansteen’s observations than by mine; 
and as he has compared the intensity at all my stations with that. 
