are more marked in interiors than on coasts. The general mean
amplitude is 12%, or, excluding exceptional districts, 24%. Regions
whose normal rainfall is small are most affected.

The following table shows the dates and characters of Bruckner's
periods:--

Warm 1746-1755 1791-1805 1821-1835 1851-1870 ..
Dry 1756-1770 1781-1805 1826-1840 1856-1870 ..
Cold 1731-1745 1756-1790 1806-1820 1836-1850 1871-1885
Wet 1736-1755 1771-1780 1806-1825 1841-1855 1871-1885

Interesting confirmation of Bruckner's 35-year period has been found by
E. Richter in the variations of the Swiss glaciers, but as these
glaciers differ in length, they do not all advance and retreat at the
same time. The advance is seen during the cold and damp periods.
Bruckner has found certain districts in which the phases and epochs of
the climatic cycle are exactly reversed. These exceptional districts are
almost altogether limited to marine climates. There is thus a sort of
compensation between oceans and continents. The rainier periods on the
continents are accompanied by relatively low pressures, while the
pressures are high and the period dry over the oceans and vice versa.
The cold and rainy periods are also marked by a decrease in all pressure
differences. It is obvious that changes in the general distribution of
atmospheric pressures, over extended areas, are closely associated with
fluctuations in temperature and rainfall. These changes in pressure
distribution must in some way be associated with changes in the general
circulation of the atmosphere, and these again must depend upon some
external controlling cause or causes. W. J. S. Lockyer has called
attention to the fact that there seems to be a periodicity of about 35
years in solar activity, and that this corresponds with the Bruckner
period.

It is clear that the existence of a 35-year period will account for many
of the views that have been advanced in favour of a _progressive_ change
of climate. A succession of a few years wetter or drier than the normal
is likely to lead to the conclusion that the change is permanent.
Accurate observations extending over as many years as possible, and
discussed without prejudice, are necessary before any conclusions are
drawn. Observations for one station during the wetter part of a cycle
should not be compared with observations for another station during the
drier part of the same, or of another cycle