rrant any general correlation and study of these facts as a whole. But
there are certain considerations which should be borne in mind in
dealing with this evidence before any conclusions are reached. In the
first place, changes in the distribution of certain fruits and cereals,
and in the dates of the harvest, have often been accepted as undoubted
evidence of changes in climate. Such a conclusion is by no means
inevitable, for many changes in the districts of cultivation of various
crops have naturally resulted from the fact that these same crops are in
time found to be more profitably grown, or more easily prepared for
market, in another locality. In France, C. A. Angot has made a careful
compilation of the dates of the vintage from the 14th century down to
the present time, and finds no support for the view so commonly held
there that the climate has changed for the worse. At the present time,
the average date of the grape harvest in Aubonne is exactly the same as
at the close of the 16th century. After a careful study of the
conditions of the date tree, from the 4th century, B.C., D. Eginitis
concludes that the climate of the eastern portion of the Mediterranean
basin has not changed appreciably during twenty-three centuries.

Secondly, a good many of the reports by explorers from little-known
regions are contradictory. This shows the need of caution in jumping at
conclusions of climatic change. An increased use of water for irrigation
may cause the level of water in a lake to fall. Periodic oscillations,
giving higher and then lower water, do not indicate progressive change
in one direction. Many writers have seen a law in what was really a
chance coincidence.

Thirdly, where a progressive desiccation seems to have taken place, it
is often a question whether less rain is actually falling, or whether
the inhabitants have less capacity and less energy than formerly. Is the
change from a once cultivated area to a barren expanse the result of
decreasing rainfall, or of the emigration of the former inhabitants to
other lands? The difference between a country formerly well irrigated
and fertile, and a present-day sandy, inhospitable waste may be the
result of a former compulsion of the people, by a strong governing
power, to till the soil and to irrigate, while now, without that
compulsion, no attempt is made to keep up the work. A region of
deficient rainfall, once thickly settled and prosperous, may readily
become an a