Lovering and Bond on Magnetic Observations at Cambridge. 55 
Philadelphia, New Haven and at Toronto, U. C. A description of its 
appearance at New Haven may be seen in Silliman’s J ournal, No. I. 
Vol. XXXIX.* Where facilities existed for making the observa- 
tions it was discovered to be accompanied with similar effects upon 
the magnetic declination as were felt at Cambridge. The Mag- 
netometer at Philadelphia experienced great derangements, although 
the limits were less, not exceeding 55.8. The influence which 
an Aurora exerts upon the earth’s magnetism reaches as far and wide 
as the appearance itself; and probably the intensity of the effect is 
proportional to the brilliancy of the display. The greatest disturb- 
ance of the Magnetometer at Philadelphia was, as at Cambridge, be- 
tween 4"and 5" A.M. Gott. M. T. The deflection of the instrument 
at Cambridge amounted to about 57 minutes, and the extremes were 
separated by little more than 2 hours. Lieutenant Riddell informs 
us that at Toronto the are traversed was 1° 59’, which was never 
equalled, and approached but once on a similar occasion. We also 
learn from him that an Aurora was noticed at Greenwich, Great 
Britain, on the same day ; but he adds, that the disturbances there 
and at Toronto were very different. 
Such full information is not possessed in regard to the Aurora of 
August 28-9. It is evident from the observations that the Mag- 
netometer at Cambridge was more affected on that day than ever 
before, the whole change of declination amounting to 61’, At To- 
ronto, where the Aurora was also seen, the disturbances were 
equally surprising and produced an oscillation of 1° 33’ in declina- 
tion. The greatest amount of derangement at Cambridge was as 
follows : 
* See also the Journal of the Franklin Institute for June, 1840, which con- 
tains some observations made upon it at Southwick, Mass. 
