FROST — PHENOLOGY 17 



ders the stationary smudge ineffective. Any sort of a fire-box that 

 can be placed on a stone-boat or sled will answer the purpose. 



The most effective method, and the one now practiced by the large 

 fruit-growers of Colorado and Cahfornia, is the distribution of a large 

 number of small fires, about forty to the acre, throughout the orchard. 

 In this case dependence is placed in the direct heat given off by the fires 

 as well as in the cloud formed from the smoke. Coal is the fuel most 

 generally used in California, while oil is coming into use in Colorado. 

 When coal is used, it is the practice to suspend wire baskets 

 a few feet from the ground, containing ten to twenty pounds of 

 coal, which is lighted when frost threatens. Forty such baskets 

 will raise the temperature of the orchard tliree or four degrees. 

 The cost depends upon the price of the fuel. In California a ton 

 of soft coal that costs $2.50 was considered sufficient for one acre 

 each night. 



Some orchardists have replaced the coal baskets with oil burners. 

 This method is more expensive to install, as the burners are more 

 costly than the baskets, and tanks must be provided for the storage of 

 the oil ; but it is said to be much more convenient, and quite as efficient. 

 At the Hamilton fruit ranch, near Grand Junction, Col., the 

 temperature in an orchard of twenty acres was maintained at 33° 

 by the use of oil burners, while a minimum temperature of 27° 

 was registered in surrounding localities. The cost of the protec- 

 tion of this orchard for four nights when frost occurred in the vicinity 

 was approximately ten per cent of the value of the crop. Methods 

 less systematic than the above are usually disappointing. (For 

 another discussion, see Paddock and Whipple, " Fruit-Growing in Arid 

 Regions.") 



Phenology 



Phenology (contraction of phenomenology) is that science which con- 

 siders the relationship of local climate to the periodicity of the annual 

 phenomena of nature. It usually studies climate and the progression of 

 the seasons in terms of plant and animal life, as the dates of migrations, 

 of blooming, leafing, ripening of fruit, defoliation, and the like. If 

 observations are to have permanent value, they must be taken with a 

 definite purpose. The particular objects of phenological obser- 

 vations are the following : — 

 c 



