le, lying about 5800 ft. above the sea near Lake
Tahoe, the lowest temperature of the year may be -25 deg. F. or colder,
when 70 m. westward at Rocklin, which lies in the foothills about 250
ft. above the sea, the mercury does not fall below 28 deg. Snow never
falls at Rocklin, but falls in large quantity at Truckee; ice is the
crop of the one, oranges of the other, at the same time. There are
points in Southern California where one may actually look from sea to
desert and from snow to orange groves. Distance from the ocean,
situation with reference to the mountain ranges, and altitude are all
important determinants of these climatic differences; but of these the
last seems to be most important. At any rate it may be said that
generally speaking the maximum, minimum and mean temperatures of points
of approximately equal altitude are respectively but slightly different
in northern or southern California.[3]

Death Valley surpasses for combined heat and aridity any meteorological
stations on earth where regular observations are taken, although for
extremes of heat it is exceeded by places in the Colorado desert. The
minimum daily temperature in summer is rarely below 70 deg. F. and often
above 90 deg. F. (in the shade), while the maximum may for days in
succession be as high as 120 deg. F. A record of 6 months (1891) showed
an average daily relative humidity of 30.6 in the morning and 15.6 in
the evening, and the humidity sometimes falls to 5. Yet the surrounding
country is not devoid of vegetation. The hills are very fertile when
irrigated, and the wet season develops a variety of perennial herbs,
shrubs and annuals.

_Fauna._--California embraces areas of every life-zone of North America:
of the boreal, the Hudsonian and Canadian subzones; of the transition,
the humid Pacific subzone; of the upper austral, the arid or upper
Sonoran subzone; of the lower austral, the arid or lower Sonoran; of the
tropical, the "dilute arid" subzone. As will be inferred from the above
account of temperature, summer is longer in the north, and localities
in the Valley have more hours of heat than do those of south California.
Hence that climatic characteristic of the entire Pacific Coast--already
referred to and which is of extreme importance in determining the
life-zones of California--the great amount of total annual heat supply
at comparatively high latitudes. A low summer temperature enables
northern species to push far southward, whi