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156 Proceedings of the British Association. 
ie 
other in all their inflexions, and differing only in the magnitude 
ef the change. This similarity had been found to extend to the 
utmost limits of Europe, and to hold at stations as remote as Dub- 
lin, Petersburgh, and Milan. It became, therefore, a question of 
great interest in the extension of this system to still more distant 
stations, to determine whether there were any and what limits 
to this accordance. ‘The question was determined by the very 
first results of the observations recently established by the British 
government, and the observations first mentioned, were selected 
as elucidating it in a very marked manner. The magnetical dis- 
turbances. which occurred on these days were among the most 
eonsiderable which had been as yet observed. .On the former 
day, (May 29, 1840,) the declination at Toronto underwent a 
sudden change, amounting to L° 52’ in about twenty minutes of 
time, while the disturbance of the horizontal force was so great — 
as to carry the magnet beyond the limits of its scale. On the 
latter day, (Aug. 29, 1840,) the greatest change of the declination 
amounted to 1° 26’ at Toronto, and to 1° 18’ at Dublin. The 
greatest change of the horizontal intensity at the former station 
amounted to .028, or about one thirty sixth part of the whole in- 
tensity: while at Dublin the change was even greater, and ex- 
tended beyond the scale of the instrument. It is probable that 
an attentive comparison of the curves may lead to many impor- 
tant results; but there are some which appear upon a cursory 
inspection, which Mr. Lloyd said he should now notice. The 
first was, that the greater magnetic disturbances appeared to be 
synchronous at the most distant stations. This important fact 
is exhibited much more evidently in the changes of horizontal 
intensity than in those of declination, and if verified by further 
comparisons, leads to the conclusion, that the principal forces 
whieh disturb. the magnetic equilibrium of the earth, are not of 
local agency. The next circumstance which merited attention 
was, that the order of the changes was no longer regulated by 
the same law at very remote stations; the representative curves 
exhibiting none of that similarity alsaady referred to, which was 
shown within the limits of Europe, and the epochs.of the sue- 
cessive maximaand minima presenting no agreement whatever: 
This important fact was first brought to light in the course of a 
series of simuult 1s, made by Prof. Bache at Phil- 
adelphia, and by himself .at Dublin, in November, 1839, in the 
