10 PRACTICAL ARBORICULTURE 
ornithology, since birds are protectors of the forests. Both these are included 
in arboriculture, which also comprises the study of those fungus and other 
diseases common to many forest and cultivated trees. 
Protection of forests from fires, how to prevent and how to extinguish them 
before too great an area shall have been destroyed, construction and maintenance 
of fire guards along natural base lines carefully prepared and managed so as to 
prevent the spread of fires which may have been started from any cause, are im- 
portant subjects included in arboriculture. 
Irrigation, which is receiving increased attention as it deserves, is subor- 
dinate to arboriculture, for without forests to protect the snowfall, preventing 
its too rapid melting, as well as to regulate the electric currents which largely 
govern the movement of clouds and precipitation of moisture, there will be no 
necessity for irrigation works, since there will be little water requiring reservoirs 
or ditches. 
History is replete with illustrations oft repeated in which nations have 
been destroyed and the people dispersed, or greatly reduced in numbers, where 
after the destruction of the forests such country became so arid and barren 
as to refuse support for the population which inhabited it. Arboriculture 
points out a way by which such disastrous results may not be visited upon 
our country. 
The planting of trees in forests, for economic reasons, on the streets and 
roadside for shade and shelter; in parks and private grounds for ornament, 
species of trees suited to various soils, altitudes, aspects and localities, are sub- 
jects pertaining to arboriculture. 
NURSE TREES. 
The influence of apparently unimportant shrubs and plants upon the nat- 
ural reafforestation of a region with more important coniferous or other trees 
upon the mountains and on the plains, is an important study. As, for instance, 
the little valued scrub oak which covers many mountain slopes prepares a special 
soil by collecting and holding its fallen leaves within its cluster of stems. 
Here the seed of fir, spruce and pine finds lodgment, germinates and is pro- 
tected from browsing animals until it has outgrown its protectors and be- 
comes the mighty tree so prized by man. 
WOOD PRESERVATION. 
The chemical preservation of timber, to increase its durability, becomes a 
highly important subject since our forests are being so rapidly depleted. The 
most economic and effectual methods of treating timbers to preserve them 
from decay, and a study of the antiseptic substances which may be thus used 
will be considered by those who are able to treat this subject intelligently. 
It was well known to the earliest nations of history that asphaltum, bitu- 
men, salt, and other material would preserve wood, flesh, cloth, and other sub- 
stances from decay, while mummies and their wrappings and wooden caskets 
have lasted through thirty centuries. 
By a proper application of this knowledge our forest products may be 
