246 Forestry Quarterly 



the degree of protection desired. The same thing might better 

 be expressed in terms of mileage of roads, trails, etc., per unit of 

 forest area. For such purposes probably the township is the 

 most convenient unit. 



At least five variables can be identified: (1) Average number 

 of fires per township to be expected and provided for, (2) total 

 acres of permissible burn per 1,000 acres and township, (3) 

 average rate of spread of fire per hour, in acres, or say, for 

 first 5 hours, second 5 hours, etc., (4) rate of practicable travel 

 by fire-fighting crew over roads, trails, across country, (5) average 

 distance to be traveled by fire crews between their headquarters 

 and the fire. Reasonably accurate figures can usually be inter- 

 polated for any given forest or township. A hypothetical case 

 for a specific township would work out as follows: (1) Number 

 of expected fires, 3, (2) allowable burn 1 : 1,000, equals 33 acres 

 per township, (3) rate of spread, first five hours covers 5 acres, 

 (4) rate of practicable travel — by motor vehicle on roads, 15 

 miles per hour, by pack train on trail, 3 miles, across country, 2 

 miles per hour, (5) average distance for crew to travel, 15 

 miles. This works out : average area of burn at time crew fin- 

 ishes work, 7-f- acres. (Allow for spread after work com- 

 mences, 2-)- acres.) Permissible area of fire when crew arrives, 

 5 acres. To maintain this record, the crew has a maximum of 

 five hours to make its trip, without allowance for margin of 

 safety. (It is assumed that the fire is promptly detected, accu- 

 rately reported by telephone from a lookout, and that the crew 

 is ready to start at once with complete equipment.) 



If there is no hitch, with an all trail route to the fire, the 

 crew will arrive in just five hours. If there is an automobile 

 road (and an automobile), the crew can be set down in one 

 hour. If there is 5 miles of good road and 10 miles of cross- 

 country travel, the crew will arrive in 5 hours and 20 minutes. 

 With 9 miles of trail and 6 miles across country, the crew gets 

 in 6 hours after the fire is reported — an hour too late. 



Working with such a formula, it is possible to approximate 

 the results to be expected with any given degree or quality of 

 improvements. It is possible to reach the same end by determin- 

 ing the greatest distance from road or trail or telephone line 

 which can be reached within reasonable time after fire is reported. 



