460 
himself, at Paris, in the year 1818, with the contempora- 
neous observations of M. Kupffer, at Casan. Not long af- 
ter, the subject underwent a fuller investigation in the hands 
of Humboldt; and, in the year 1827, an extensive system of 
simultaneous observations was organized by that illustrious 
philosopher for the purpose of elucidating it. At length, 
in 1834, it was taken up by Gauss, and received a much 
greater development. Gauss discovered that the irregular 
changes of the declination were of continual occurrence ; 
and that the synchronism, which had been previously ob- 
served only in the larger changes, extended to the minutest 
movements. In order to investigate the law of these syn- 
chronous changes, and the locality and other circumstances 
of the acting forces, Gauss arranged the extensive plan of 
simultaneous observations at short intervals, which has been 
already four years in operation, and in which almost every 
country in Europe has been represented by some one or 
more observers. 5 
Having taken part in this combined system in the year 
1837, Prof. Lloyd was led to inquire, in the first place, whe- 
ther this irregular fluctuation of the declination might not be 
still more rapid than appeared from the observations hither- 
to made; and, secondly, whether these shorter oscillations (if 
they existed) corresponded in distant places, and could 
therefore be employed to determine differences of longitude. 
To investigate the first of these questions, a series of 
observations was made in the month of September, 1837, at 
very short intervals. The instrument employed was Gauss’s 
magnetometer ; and the magnet being in a state of continued 
vibration, observations were taken at each succeeding maxi- 
mum elongation, and therefore at the interval of a single 
oscillation,—which, in the case of the bar employed, was 
278.38. The mean of each successive pair of readings was 
then taken, to eliminate the mechanical oscillation, and the 
results projected in curves in the usual manner. On an 
