272 SYLVICULTURE IX THE TROPICS pt .it 



that the first firing will sweep them clean. There are 

 very few lines on which the grass will dry homogeneously; 

 small depressions in the ground, which during the wet 

 weather may serve as overflow channels for carrying off 

 the water, or small pans in which the water has stood 

 longer than elsewhere, or which are the recipients of 

 heavier dew, may contain grass which remains green 

 much longer than that on better drained soil. If there 

 is much of this grass the firing may be somewhat 

 delayed, but it must be remembered once again that the 

 strength of a chain is that of its weakest link, which in 

 this case is represented by strips of dry grass running 

 across the width of the line, and that fires have a way 

 of discovering these weak links and of breaking through 

 them. If, therefore, there is any danger of fires coming 

 in from outside, firing of the lines may be commenced, 

 all the dry portions being burnt at the first firing, the 

 green patches being dealt with afterwards as soon as 

 they are dry enough to burn. Sometimes the wither- 

 ing heat of the flames dries even fairly green grass 

 sufficiently for it to be consumed even at the first firing, 

 and a certain amount of help can be given to them by 

 widening the guide-lines at these points, and thus throw- 

 ing a thicker cushion of inflammable grass on the edges 

 of the trace. By pressing or rolling the grass down it 

 is also more easily set on fire. 



If the traces have been cleared of trees and other 

 woody growth, it generally happens that the grass on 

 them dries earlier than in the forest, and that the firing 

 can be started while the latter is still moderately green, 

 and that the danger of fire entering into the forest 

 during: the firing of the trace will be minimised. Still, 

 this is a factor that can be relied on by no means in 

 every case. In forests composed of trees with light 

 foliage and which are shade-avoiding, as e.g. several 

 species of Acacia, or in savannah-forests, the grass out- 

 side the lines becomes inflammable practically as soon as 

 that on the lines ; and in cases where the forest has 

 been successfully protected against fire for one or more 



