420 FIRE-CONSERVANCY. 



dually burn for a long time, so that they are often carried up and 

 dropped in an ignited condition a considerable distance off, some- 

 times beyond even 200 yards. And so on. 



(^5) Violence and constancy of the wind. The actual burning of 

 the dry grass and leaves converts a mild breeze into a high wind, 

 and a brisk wind into a gale. A steady wind drives the long 

 tongues of flame along the ground, and creates a lateral blast of 

 such intensity as to set fire to grass even a hundred feet beyond 

 the visible reach of the flames. 



{6) Absence or lightness of dews. The severest forest fire will 

 at once of itself go out at nightfall where heavy dews prevail. 

 In sheltered situations, in the cold weather, dew may begin to form 

 even before sundown and not be evaporated until past noon. la 

 some places in India dews prevail right through the rainy 

 season and on to the end of April and even the middle of May, 

 and are, for many months, so heavy that the trees drip all night 

 long and during the early morning, in the same manner as after 

 an abundant fall of rain. In other places, at the extreme end of the 

 scale, they are never heavy and are limited, outside the rainy 

 season, to the three or four months following the close of the S. W. 

 Monsoon. 



(7) Heat of the sun. Where the sun is powerful, the grass 

 dries up early, dews are light, begin to be deposited late in the 

 evening, are quickly evaporated, and prevail during a limited time 

 of the year. The heat also directly assists a conflagration. 



(8) Sloping ground. Fire naturally progresses most rapidly 

 up a slope, and more rapidly the steeper the gradient is, provided 

 of course the ground is not so steep as to be unable to bear a com- 

 plete crop of grass or to support a thick continuous mass of dead 

 leaves. On the other hand, burning fragments roll or slip down a 

 slope, and thus aid the rapid spread of fire as well as render its 

 extinction on the lower side of the slope extremely difficult. On 

 a declivity dead twigs, leaves, &c., accumulate against the upper 

 side of the foot of the trees, and, in burning themselves, char and 

 kill that side of the stems, the fire often working its way through 

 far enough to bring down a tree. 



(9) Nature of the component species. Some trees take fire, 

 even in a green state, more easily than others ; some suffer less 

 direct damage or recover more readily and completely than others; 

 and so on ( see pp. 36-42 ). The resinous cones of conifers can 

 carry down fire over a whole hillside. Hollow bamboos in com- 

 bustion burst with great violence, and in Berar burning fragments, 



