weather. Climatology is the study
or science of climates.

_Relation of Meteorology and Climatology._--Meteorology and climatology
are interdependent. It is impossible to distinguish sharply between
them. In a strict sense, meteorology deals with the physics of the
atmosphere. It considers the various atmospheric phenomena individually,
and seeks to determine their physical causes and relations. Its view is
largely theoretical. When meteorology (q.v.) is considered in its
broadest meaning, climatology is a subdivision of it. Climatology is
largely descriptive. It aims at giving a clear picture of the
interaction of the various atmospheric phenomena at any place on the
earth's surface. Climatology may almost be defined as geographical
meteorology. Its main object is to be of practical service to man. Its
method of treatment lays most emphasis on the elements which are most
important to life. Climate and crops, climate and industry, climate and
health, are subjects of vital interest to man.

_The Climatic Elements and their Treatment._--Climatology has to deal
with the same groups of atmospheric conditions as those with which
meteorology is concerned, viz. temperature (including radiation);
moisture (including humidity, precipitation and cloudiness); wind
(including storms); pressure; evaporation, and also, but of less
importance, the composition and chemical, optical and electrical
phenomena of the atmosphere. The characteristics of each of these
so-called _climatic elements_ are set forth in a standard series of
numerical values, based on careful, systematic, and long-continued
meteorological records, corrected and compared by well-known methods.
Various forms of graphic presentation are employed to emphasize and
simplify the numerical results. In Hann's _Handbuch der Klimatologie_,
vol i., will be found a general discussion of the methods of presenting
the different climatic elements. The most complete guide in the
numerical, mathematical and graphic treatment of meteorological data for
climatological purposes is Hugo Meyer's _Anleitung zur Bearbeitung
meteorologischer Beobachtungen fur die Klimatologie_ (Berlin, 1891).

Climate deals first of all with _average_ conditions, but a satisfactory
presentation of a climate must include more than mere averages. It must
take account, also, of regular and irregular daily, monthly and annual
changes, and of the departures, mean and extreme, from the average
conditions which