. Bulletin (Pennsylvania Department of Forests and Waters), no. 35. Forests and forestry. K o C o • fc 1 tlie wind is blowing. If nu wind was blowing at the time of starting it is not long until the fire itself creates a draft and it travels most rapidly in the direction of the draft. More or less of an oval form is assumed and sooner or later a V shape. The side lines develop at an angle with the wind or draft and burn more sl(jwly. If much wind is i)resent the windward side may die out entirely. As the facte)i-s vary, the shape of the fire varies according to the resultant of their forces. A
. Bulletin (Pennsylvania Department of Forests and Waters), no. 35. Forests and forestry. K o C o • fc 1 tlie wind is blowing. If nu wind was blowing at the time of starting it is not long until the fire itself creates a draft and it travels most rapidly in the direction of the draft. More or less of an oval form is assumed and sooner or later a V shape. The side lines develop at an angle with the wind or draft and burn more sl(jwly. If much wind is i)resent the windward side may die out entirely. As the facte)i-s vary, the shape of the fire varies according to the resultant of their forces. As for example the apex or head may be acute or broad, according to wind, fuel, or slope. A change in topog- raphy or in wind may result in the development of several heads, or ; Other things being equal the severity of the tire depends upon the quantity and kind of fuel in its path, but necessarily the amount of moisture in the material determines the amount of fuel available for the fire. Dry material will burn readily and the heat from this fuel will dry out additional stulY rendering it inflammable. But the heat may not be sufficient to dissipate the moisture from all the litter, consequently a part may be saved and the severity of the fire lessened to that extent. The accumulation of undecayed leaves depends upon the species, sea- son, soil, exposure, and length of time since previous fire or litter removal. Species having large crowns and large leaves, such as maples and oaks, make a heavier litter than ash and birch. A layer of resinous needles burns more rapidly and with a hotter fire than does a layer of hardwood leaves. In some forests there is a varying amount of dead wood made up of standing dead trees or snags, fallen trees, dead branches, slashings, or the debris of previous fires. Any of this material in a dry condition means additional fuel and greater severity for a fire. A surface fire runs up hill rapidly because heated air currents draw flames
Size: 1238px × 2018px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectforests, bookyear1923
