D 
COVER TYPE AND FIRE CONTROL 29 
final acreage of the chaparral fire is likely to be much the larger of 
the two, for the reason that line construction is easier in the grass- 
land than in the chaparral and the race between line construction 
and creation of new perimeter by the fire will be most rapidly won 
in grassland. A factor in difficulty of control which directly affects 
final acreage is the intensity of heat, which depends upon quantity 
and inflammability of fuel present, irrespective of other topographic 
or climatic conditions. On the grass fire the crew will be able to 
work close to the edge of the flames, thereby holding the amount of 
line to the minimum. On the chaparral fire, however, the heat of 
the flames will force the crew to drop back some distance from the 
burning edge, and thus the length of line to be constructed and 
the final acreage will be increased. 
ACRES BURNED PER HOUR OF ELAPSED TIME 
a RISK ros ISIl— fsa 
Wl 
ALL TIMBER TYPES ° Vl 
See anon ITI ao Soh edn i ae MMMM ae 
BRUSH LIL es aT | 
ee ial 
Sse enaP aT: 
16 
ACRES PER icon 
AVERAGE ELAPSED TIME PER FIRE 
GENERAL RISK FIRES, ISI1I—1920 
ie aid NS ta Beene ie wigs ey 370) eae! 
auL TIMBER TvPES W////ff MMM 
woootann. -s«WV GLLWq@€EezM 
BRUSH WW WL. TTT}. 
Lee | Baa ae oars Eee c ea ara ea 
ine AGERE WEC@CECEECECEEEETF 
SUGAR PINE-FIR Ce eA SS es ee 
pouscas Fir, ik ©X~=22WRNriMH(<aQ@xaur_vn@o@wywvu WW) 
teamhaa tO cea ae] eee Pears eeeieey aoeer ees emer Seal eas) 
Ss 10 15 
HOURS 
ACREAGE AVERAGE FIRE 
GENERAL RISK FIRES, I9I1I-1920 
mon vees agai] | | || 
ALL TIMBER TYPES _(WYYYYYf 
CHAPARRAL GRASS V/HAH/H/H/M HHT) 
EERO Tee eee ieee eae 
BRUSH MMM 
veutow FINe= WY. 
2 ane ZZ 
oe ed 
FiGURE 8.—Measures of fire hazard, gereral-risk fires, 1911-1920 
The lowest and highest values of the index figures are 1.07 for the 
fir type and 55 for “the chaparral. In a broad way these figures 
mean in terms of fire control that with equal speed of attack (i. e., 
intensity of protection or hour-control) fifty times as many acres 
per hour will be burned over in the chaparral as in the fir type. Put 
