MARYLAND GEOLOGICAL SURVEY 465

TABLE VI.
Showing the secular change in the magnetic declination at various stations.

[See page image for table]

between 1580 and 1812, in an interval of 232 years, the compass
direction at London veered from 11° east to 24° 12' west, or changed
its direction by 35° 12'! A street a mile long, laid out in London
in 1580 so as to run parallel to the direction pointed out by the
compass would be 8725 feet, or -fa of a mile, too far to the east at the
north terminus according to the compass direction of 1812!

By looking over the figures for Paris and Rome we find similar
changes to those at London. At Paris the maximum easterly decli-
nation of 9° 36' was reached near the year 1580, and the maximum
westerly decimation of 22° 36' in about 1809, the needle pointing due
north in 1664. At Rome the declination of the needle reached its
maximum amount east, 11° 36', in 1570 approximately, and its maxi-
mum amount west, 17° 06', in about 1810, coinciding with the true
meridian in 1660. At Manila, on the Philippine Islands, the needle
changed from 1l' east in 1800 to 48' east in 1890, and at San Fran-
cisco, Cal., from 12° 36' east in 1780 to 16° 4l' at the present time.
We next come to Baltimore and find that at this station between 1640