26 Lovering and Bond on Magnetic Observations at Cambridge. 
nity of discovering the extent of extraordinary disturbances. Now a 
glance at the Plate betrays wonderful concert in the motions of the 
two remote bars; almost every digression of the bar at Cambridge 
and every change of curvature in the magnetic curve of that place 
has something corresponding to it in the curve of Toronto. ‘There 
are a few singular exceptions ; and, in a word, the bar at Toronto 
seems to have been more agitated and to have made greater excur- 
sions. But these discrepances throw no doubt on the subject; for 
they are just such as must be expected to occur in results which 
depend upon complex and multiform agents. A general and not a 
mathematical agreement is all that can be expected. The times 
which mark the limits of the eastern and western excursions in this 
fluctuating motion of the bars agree with great precision, except in 
two or three instances where the Cambridge curve lags behind five 
minutes or less. The parallelism appears at once from considering 
that the two curves, starting from points 12 minutes apart and 
making several digressions the same way of greater amount than 
the original arc of separation, do not cross each other except once ; 
and this solitary instance will hardly be regarded as a transgression 
of the rule, since it arose simply from one bar being more affected by 
a particular wave of the magnetic tide than the other bar. On Plate 
IL. is described the diurnal curve for the May Term-day. This too 
is singularly disturbed from 11 P. M., Gott. M. T. till 10 o’clock of 
the next morning. We have had an opportunity of comparing this 
with the similar curve observed by Professor Bache at the Girard 
College, in Philadelphia, and here again the instances of agreement 
make a stronger impression than the rare cases of discrepance. The 
correspondences are frequent and imposing ; while the points which 
exhibit no such coincidence are few and of less importance. The 
agreement as to time is in almost every place precise ; the disagree- 
