CLIMATF, AND FOREST I'IRICS 970 



4. In fire protection, clear weather in late fall may result in the 

 rapid drying out of litter, even at high elevations and after it has been 

 saturated by over an inch of rain. 



5. Air-dry litter has the property of taking up moisture from the 

 air, chiefly at night, to the extent of 5 to 6 per cent of its own weight. 



6. A study of the factors influencing the dryness of litter, namely, 

 evaporation, mind movement, relative humidity, and temperature, 

 shows that they all have the same seasonal and' diurnal maxima and 

 minima. 



7. Rate of spread of fires is best measured by size of perimeter, 

 rather than by linear distance traveled or by area covered. 



8. For slowly spreading fires, size of perimeter based on elapsed 

 time is an arithmetical progression, while with more rapid spread it 

 tends to become a geometrical progression. This is due, in part, to 

 changes in the shape of fast spreading fires and, in part, to the creation 

 of a draft by the fire itself. 



9. Rate of spread, as governed by wind velocity, may be stated to 

 vary as the square of the velocity. 



