PROCEEDINGS OF THIRTY-SIXTH FRUIT-GROWERS ' CONVENTION. 141 



mental records, such as are given by the thermograph and hygrograph, 

 the importance of which data will be apparent from the discussion 

 further on. 



Under the second head, we must discuss some of the physical processes 

 operative in the formation of frost and then mention the various devices, 

 such as smudging outfits, coal baskets, oil pots, orchard heaters, anti- 

 frost covers, etc. Opinions will differ as to the relative efficiency of 

 various devices, and some are undoubtedly more serviceable for cer- 

 tain localities than others. We propose to discuss the principles rather 

 than individual devices. 



There are three general principles used in frost-protection devices : 



1. Adding heat. 



2. Saving heat. 



3. Mixing, or stirring the air to prevent cool areas. 



Under the first are included all the various forms of heating devices, 

 such as open fires, smudge fires, coal baskets, oil pots, orchard heaters, 

 etc. The use of fires probably dates back beyond our memory, but the 

 first use of the coal baskets for the specific purpose of preventing loss 

 by frost was by Edward Copely at Riverside, Cal., about 1896. The 

 first use of oil that we have a record of was by Everett at Arlington. 

 Cal., and the first use of hot water was by Meacham at Riverside. A 

 severe frost about the end of December, 1905, caused great damage to 

 the orange crop in the Riverside section, and the following year may 

 be said to have marked the beginning of the frost fighting campaign. 

 The Riverside Horticultural Club took an active interest in the problem, 

 and many experiments were conducted by such men as those already 

 mentioned and Koethen, Reed, Holmes, Hall,* Hammond, and McAdie. 

 The work has gone on and there are now on the market many forms of 

 heating devices. A convenient and serviceable frost alarm thermometer 

 and oil pot were devised by the "Weather Bureau official at Fresno. 

 Cal.. Mr. J. P. Bolton, for use in the vineyards during the spring frosts. 

 There have recently been put upon the market orchard heaters, burning 

 oil. and the claim is made that in the apple sections of Colorado and 

 other Rocky Mountain states results have been most satisfactory. These 

 are known as the Troutman Orchard Heaters, burning oil, and used 

 variously, forty to a hundred to the acre. 



Direct heating by large open fires is not recommended, as experi- 

 ence has shown that the heat is radiated largely upward and is not 

 effective in warming the fruit. I may illustrate this by the following 

 experience of one of the most intelligent horticulturists in California. 

 Mr. J. S. Douglass of San Emigdio Ranch writes that during the night 

 of December 20 and 21. 1908, the temperature for fourteen hours 

 ranged between 19° to 24° F. For thirty-six hours the temperature 

 did not rise about 28° F. About fifteen cords of wood and forty tons of 

 wet hay were burned in the effort to protect the orchard. The relative 

 humidity was low. there was little air movement, and the smoke rose 

 as straight as a pine tree. At the intersection of two roads in the 

 orchard there was a large fire and thirty feet away a thermometer was 

 placed on an olive tree. A second fire was burning twenty feet away 

 from this tree in another direction, and a third fire twenty-five feet 

 away in still another direction. The temperature at the tree, however, 



''And others whose names I can not now recall. 



