LOCALISATION OF INTERNAL PIRE3. 425 



niug fire-l>reaks along the face of a hill or along the bottom of a 

 narrow ravine or valley. It is needless to say that cliffs should 

 generally be avoided, tor if on the one hand, fire could not possibly 

 climb up from below, on the other hand, there would always be the 

 risk of burning brands and other fragments being blown down 

 from above, unless a very broad fire-trace were cleared, or a suffi- 

 ciently wide belt of some evergreen shrub, tree or climber grew 

 along the upper edge of the cliff. 



Although a truism, still it is necessary to add that at no point of 

 the length of a water-course, too narrow to serve by itself as a 

 break, ought more than one bank to be fire-traced. As regards a 

 road both or only one side of it should be cleared of combustible 

 matter according as it is a frequented public thoroughfare or the 

 traffic is light or strictly regulated ; and when only one side is 

 fire-traced, it should be that from which the wind blows. It is 

 obvious that the more nearly perpendicular to the direction of the 

 strongest winds a fire-break is, the broader must it be. Hence 

 in the interests of economy, if artificial breaks are in question, they 

 should diverge from that direction as much as the topography 

 system of export, the shape and lie of the forest, and other 

 prevailing conditions will allow. 



The smallness and hence the number of the fire-blocks will be 

 directly proportionate to the value of the standing stock, to the 

 intensity of treatment to which the forest is subjected, to the ease 

 and inexpensiveness with which the division can be effected, to the 

 amount of traffic passing through the forest, and to the difficulty 

 with which, owing either to insufficiency of labour or inaccessible 

 ground or to the conditions described on pp. 417-21, conflagrations 

 can be put out. The size of the blocks in different forests will 

 thus be very different, but as a rule it ought not to exceed 10 square 

 miles in remote forests of no great value or 1000 acres in valuable 

 forests on which there is an active demand. Except in small 

 coppices, in which each annual coupe will generally form a separate 

 block, a smaller minimum than 200 acres will seldom be required. 



The width of the intervening fire-trace may be insufficient to 

 prevent in all circumstances fire from crossing over from a burning 

 block to the next one ; and even if the width is in itself sufficient, 

 the trace may not at the time be effective, because of fallen dead 

 leaves strewing it or from its not yet having been completely 

 cleared, or for any other reason. In such a contingency, if the 

 conflagration cannot be put out before it reaches the trace, the 

 only plan to follow is to fire the grass along the trace in the burn- 



