4 Transactions.— Miscellaneous. 
maximum of 24° 41’ was reached. Since then it has gradually diminished : it 
was 22° 30' in 1850; in 1866, 20° 25’; and is probably at the present date 
some few minutes under 20? W. 
The annual variation at Paris and London is greatest about the latter end 
of March in each year, diminishing from that time to the latter end of June, 
and increasing agam during the following nine months. It does not exceed 
from ‘15’ to 18’, and it varies somewhat at different epochs. 
The diurnal variation differs according to the time of year and place of 
observation, the mean daily range in London being about 9-3 minutes ; in 
Paris, about 11:5 minutes. The amplitude of the daily variations is greatest 
from April to September. 
The declination is accidentally disturbed in its daily variations by many 
causes, such as earthquakes, voleanic eruptions, and the aurora borealis and 
aurora australis. In Ganot's * Elements of Physics" it is said that “the effect 
of the aurora is felt at great distances. Auroras which are only visible in the 
north of Europe act on the needle even in these latitudes (that is, of London 
and Paris), where accidental variations of 20’ have been observed, In polar 
regions the needle frequently oscillates several degrees ; its irregularity on the 
day before the aurora borealis is a presage of the occurrence of this 
phenomenon.” Although there is little doubt that the declination of the 
needle is generally affected to a greater or less extent before and during the 
aurora, yet this is not invariably the case, as the following extract from 
Captain Parry’s narrative of his third voyage for the discovery of a north-west 
passage will show, The extract is so short and so pertinent to the subject 
under consideration that I make no apology for introducing it. Speaking of 
the aurora borealis, he says :— 
“ About midnight on the 27th of January, 1825, this phenomenon broke 
out in a single compact mass of brilliant yellow light, situated about a south-east 
bearing, and appearing only a short distance above the land, This mass of 
light, notwithstanding its general continuity, sometimes appeared to be 
evidently composed of numerous pencils of rays, compressed, as it were, 
laterally into one, its limits, both to the right and left, being well defined and 
nearly vertical. The light, though very bright at all times, varied almost 
constantly in intensity, and this had the appearance (not an uncommon one in 
the aurora) of being produced by one volume of light overlying another, just 
as we see the darkness and density of smoke increased by cloud rolling over 
cloud. While Lieutenants Sherer and Ross and myself were admiring the 
extreme beauty of this phenomenon from the observatory, we all simultaneously 
uttered an exclamation of surprise at seeing a bright ray of the aurora shoot 
suddenly downward from the general mass of light, and between us and the 
land, which was then distant only three thousand yards. Had I witnessed 
