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OUR FORESTS 21 
- now serve numerous other purposes and in 1941 yielded raw materials 
worth about 18 million dollars. 
Not so valuable commercially, but with a domestic importance all 
their own, are the sugar and sirup made from the sap of the sugar 
maple and its close relative, the black maple. The trees are tapped 
in February or March by boring small holes in the sapwood. A spout 
is inserted in each hole and a bucket hung beneath it to catch the sap 
which drips out. The collected sap is carried to the sugar house, 
where it is boiled down to the proper consistency for sirup or sugar. 
Most of the maple products come from the Northeastern and North- 
ern States, but a few other States also produce them in commercial 
quantities. 
There are also numerous other forest products of more or less im- 
portance. The bark blisters of the balsam fir produce a resin which 
when refined has sold for as much as $40 a gallon in recent years. In 
spite of all the work and skill of the chemists, wood and bark remain 
the chief sources of tannins; and dyes from various trees, such as black 
oak and Osage-orange, are still to be found in trade channels. Many 
kinds of edible nuts and fruit, crude drugs, and Christmas greens also 
come from our forests. 
FoRESTS AND Our WATER SUPPLY 
Forests give invaluable service to man through the protection of 
watersheds and the regulation of stream flow. The thick crowns of 
the forest trees, which sometimes almost entirely shut the sunlight 
from the forest floor, also break the fall of the rain. Down on the 
forest fioor the water from rain or melting snow is likewise inter- 
cepted by the leaf litter. It sinks gradually into the soft absorbent 
soil beneath, and some of it eventually finds its way underground to 
the springs and streams (fig. 18). The checking of surface waters 
tends to make stream flow regular and continuous throughout the 
year. Where watersheds are not protected, rains fall on bare soil, 
and the water rushes down the slopes, with the result that streams 
rise quickly to flood height and as quickly dwindle away. 
Adequate watershed protection insures an abundance of water for 
use in homes, for irrigation of cultivated lands, and for river naviga- 
tion. It helps to make constant the power which turns the wheels 
of many a factory and furnishes electric current for numberless uses. 
It keeps the rains from washing away huge quantities of rich soil, 
leaving hillsides bare and unproductive and chocking river beds and 
bottoms with heavy deposits of mud. 
One-half of our forest area exercises a major influence on stream 
flow and an additional quarter a moderate influence. The area of 
major influence, however, feeds streams that flow through nearly 
every other part of the country. Therefore, practically our entire 
population directly or indirectly benefits from forest-protected waters. 
OTHER USES OF THE FOREST 
Forests have still other protective uses. They help to prevent land- 
slides and snowslhides; they protect homes, fields, and orchards from 
cold and destructive winds; and in some parts of our country they 
give permanent form to sand dunes, which otherwise would be con- 
