250 M. Kreil’s Magnetic Ohsermtions. 
tends also to the total force. The needle in our inclina- 
torium completes one vibration in nearly 14? seconds : during 
the disturbance of the 17th of January 1838, it underwent an 
alteration of 0^'*074^. In February of the same year the mean 
of the observed times of vibration for the month was 13"*874, 
but for the 21st day of the month it was 13*932. I need not 
remark how important it would be to examine such kindred 
phaenomena as those of the atmosphere and auroras, with the 
same exactness which is now applied to magnetic investi- 
gation. 
I must mention one other phsenomenon which claimed our 
attention in a very high degree, and which perhaps may 
deserve that of other observers. I mean the vertical oscilla- 
tions which show themselves so often in the dipping-needle, 
and which also appear to be connected with determinate laws. 
At least they are much more frequent in November and De- 
cember than at other seasons, and they occur most commonly 
in wet weather. For this reason I do not think that they can 
be ascribed to a tremulous motion of the building, from which 
the part of it which contains the apparatus is quite free. 
Neither can they be attributed to the effect of currents of air, 
because they occur less frequently at the time of the equi- 
noctial gales and other storms than at the above-named 
times. Perhaps they arise from very weak shocks of earth- 
quake, which may be revealed to us by this highly sensitive 
apparatus, and which probably occur much more frequently 
than the more considerable shocks which are recognised by 
our senses, and by other effects. At least the greatest vertical 
oscillations of the needle have almost always coincided with 
considerable earthquakes, often having their seat in remote 
countries. One striking instance of this kind, after we had 
experienced other similar ones, occurred on the 23rd of Ja- 
nuary 1838. Between 7^ 33’“ and 7’’ 4?7^“ p.m., Milan mean 
time, the needle began to oscillate so strongly that its arc of 
vibration appeared, by the vertical scale attached, to amount 
to 27 millimeters, or nearly 10 minutes of arc; there were no 
other indications of an earthquake of any kind. Twenty days 
afterwards the newspapers contained accounts of considerable 
damage caused by an earthquake on the same evening at 
Bucharest, Jassy, Odessa, and other places. According to 
these accounts the shock was felt at Jassy at 7’^ 4?2% and at 
Odessa at 7^ Milan mean time, agreeing with the beginning 
of the phaenomenon observed by us. 
Milan, Jan. 9, 1839. 
