FROST 
that the English walnut is tender, and 
the wood was badly injured by the freeze. 
Pear trees were comparatively hardy, 
about a medium between peaches and 
apples, or perhaps a little nearer ap- 
proach to the apple. Plums were not 
hardy; there was a fair crop of prunes 
and but few apricots, as the wood was 
not hardy. Pears were heavily loaded 
with bloom and bore a good crop. 
The effects of rain or extra humidity 
should be remembered when considering 
the resisting power of a tree or plant. 
It is the same as with animal life. If ex- 
posed to rain, the body radiates heat 
much more rapidly than if it is kept per- 
fectly dry. As has already been remarked, 
plants do not respond so sensitively to 
these changes of temperature as do ani- 
mals, but any person knows that he has 
less power to withstand the cold if his 
clothes are wet than if they are dry. It 
is so with plants. If a cold wave follows a 
shower of rain, plants are much more 
sensitive to the cold and in much more 
danger of being killed than if the atmos- 
phere is dry. The degree of vitality, 
also, in a plant has much to do with de- 
termining its resisting power. 
Conditions Which Affect the Frost 
Problem 
There are three conditions that affect 
the frost problem. The first is eleva- 
tion; the second is air drainage; the third 
is evaporation, usually from large bodies 
of water, which tend to modify the tem- 
perature. 
In rough or hilly country there will be 
what is known as thermal belts, usually 
following the contour of the hills. Low or 
pockety lands will be relatively cold while 
higher situations above the level of the 
natural air outlets will be relatively 
warm and orchards situated on this high- 
er land will not be so liable to suffer 
from frosts. 
There are valleys that are often called 
lowlands through which the air currents 
sweep with force enough so that there is 
seldom frost to injure the vegetation. 
Reference has already been made to pro- 
tection by lakes, bays, inlets or bodies of 
water that modify the temperature Even 
2—23 
1009 
several miles inland this is often true. 
For instance, the prevailing winds from 
the Pacific ocean are generally from the 
west or northwest. These winds are ob- 
structed by the Cascade mountain range 
so that the territory along the foothills 
on the east side of the mountain range 
is more or less protected from the winds, 
but there are mountain passes like the 
Cowlitz pass, for instance, through which 
these winds sweep with considerable 
force. The air currents coming through 
the Cowlitz pass and sweeping down the 
Naches valley, which is part of the 
drainage system of the Yakima and Co- 
lumbia rivers, modifies the temperature 
in the Naches valley so that, while the 
valley itself is not at a higher elevation, 
only being about 1,100 to 1,500 feet above 
sea level, yet they are seldom injured 
by frosts, while the lands in the Ahtanum 
valley, only a few miles separated from 
the Naches and on substantially the 
same level, but sheltered from the winds 
of the coast by a higher elevation of the 
mountain, generally are not quite so well 
protected from frosts and ordinarily 
there will be a little more danger to 
fruit crops in the Ahtanum valley on 
a general elevation than in the Naches; 
but there have been notable exceptions. 
One of these exceptions was in April of 
1911, when a cold current of air came 
down from the north and settled in the 
Naches valley, and did as much damage 
or perhaps more than in some of the 
other valleys on the same level. There 
are exceptions to the general rules grow- 
ing out of the changes in the direction 
of the wind, but the fact still remains 
that wind currents have much to do in 
preventing the settling of frosts upon 
the earth’s surface. 
The question of how the higher altitude 
furnishes better protection from frost 
than the lower is one about which a 
great many persons inquire. We can 
perhaps better answer this by saying 
that we are living upon the bottom of an 
ocean of air very like the ocean of wa- 
ter in which living creatures breed and 
grow. This ocean of air is not less than 
fifty miles deep, and is perhaps much 
deeper than that. One law of this at- 
