272 REPORT OF STATE BOARD OF HORTICULTURE. 



air at times of danger. From what the writer is able to learn he does not 

 think the trials of the damp smudge were generally made in the most effi- 

 cient manner ; however, in very dry climates, the vapor of the wet smudge 

 diffuses throughout the surrounding space without condensing, thus render- 

 ing that method of protecting inefficient. 



MIXING THE AIR SO AS TO PREVENT THE COLD AIR FROM SINKING TO 



THE SURFACE. 



While many of the preceding methods depend partly on this principle 

 for their success, the writer is not familar with any process which depends 

 solely upon it. 



WHEN AND HOW TO PROTECT. 



The experience of the past two seasons has shown that forecasts of sud- 

 den and decided changes in temperature over a large territory are among 

 the most accurate made by the Weather Bureau : consequently, it is reason- 

 able to expect that, if suitable arrangements are made, warnings may be 

 received of those otherwise unexpected cool waves, which will result in 

 frost. There are instances, however, when the general forecasts of the 

 Weather Bureau cannot be expected to b» sufficiently specific to provide for 

 the different conditions that may prevail in various sections. The temper- 

 ature frequently remains for several days near the critical point, and a 

 change of a very lew degrees or a local clearing or clouding of the sky will 

 cause or prevent injury. Again, the conditions in certain localities are such 

 as to make them more susceptible to frost than the surrounding region. 

 Prof. Willis L. Moore. Chief of the Weather Bureau, states that, while fore- 

 cast official in Wisconsin, he observed that a frost occurring immediately 

 after a rain was not as injurious as when the ground and plants were dry. 

 It is therefore necessary that the orchardist and gardener be able to judge, 

 at times, for themselves when frost is imminent. For this purpose they 

 should be provided with a wet and dry-bulb hygrometer, by which can be 

 determined the dew-point of the air or the tempei'ature at which condensa- 

 tion takes place. Condensation checks the fall in temperature on frosty 

 nights. Frequent observations with this instrument should be made. 



If, in the afternoon, the dew-point is near the critical temperature, 

 arrangements should be made for protecting, if necessary. If, at a later 

 hour, the dew-point is constant or lowei-, the sky clear or clearing, and the 

 air calm, it is reasonable to expect that the temperature will fall to the dev.- 

 point during the night. The efforts to protect should be based on this dew- 

 point. If it merely approximates the danger point ( and no warning of 

 more severe temperatures has been received ) but little protection will be 

 necessary, and action may be delayed until the temperature is Vjut a few 

 degrees above the danger point. However, if the dew-point be several 

 degrees below that liable to cause injury, or if it be falling, or if a change 

 for the colder be anticipated, efforts to protect should be undertaken 

 earlier. 



No specific rules of universal application can be laid down for the guidance 

 of the orchardist in jirotecting. The same intelligent, careful, and sys- 



