274 REPORT OF STATE BOARD OF HORTICULTURE. 



tected hillsides displaces that which has been kept warm, and, should wind- 

 breaks be found successful in removing this danger, it is believed there are 

 few, if any, localities where injury could not be avoided. 



It is evident that in attempting to protect one ranch the owner will, in a 

 measure, protect his neighbor ; therefore, if some arrangements for co-opera- 

 tion among the individuals in the same locality were made, the greatest pro- 

 tection could be provided at the minimum expense. By such a co-operation 

 of all the residents of the valley, a system of windbreaks or air-drainage 

 dikes (if found valuable) could be laid out and built in such a manner as to 

 result in the greatest general good at the least cost. Arrangements could 

 be made which would insure the distribution of a frost warning from the 

 Weather Bureau throughout the entire district. Some person, provided with 

 a telephone, could receive the warnings from the bureau, and, in turn, tele- 

 phone them to all others having such instruments. All so receiving them 

 could display the frost signal, and thus the warning would be quite gener- 

 ally distributed. 



Some person in each locality or ranch should study the peculiarities of 

 his section. He should thoroughly understand the conditions under which 

 frost forms, should provide himself with a psychrometer, and take frequent 

 observations on afternoons and evenings when frost is imminent, and thus 

 be enabled to give the most acciirate information possible to his locality. 

 He would probably thus prevent the inconvenience and expense connected 

 with protecting when the local conditions or a change in the weather were 

 such as would prevent a frost, and also he would be likely to discover times 

 when frost was imminent when no warning had been received. This man, 

 indeed, should be a sort of local expert on this subject. 



THE USE OF THE SLING PSYCHROMETER. 



This instrument is a form of hygrometer most suitable for the use of the 

 orchardist. It consists of two thermometers fastened to the same back and 

 arranged for whirling. One of the thermometers has its bulb covered with 

 thin muslin, moistened with water. The evaporation of the water about the 

 wet bulb lowers the temperature and causes this thermometer to read lower 

 than the one with a dry bulb. From the difference between these readings 

 and the temperature of the air itself the dew-point can be quite accurately 

 determined from the accompanying table. 



Exposure — While the psychrometer will give quite accurate indications, 

 even in the bright sunshine, yet observations so made are not without some 

 error, and where greater accuracy is desired the psychrometer should be 

 whirled in the shade of a building or tree, or, as may sometimes be necessary, 

 under an umbrella. In all cases there should be perfectly free circulation of 

 the air, and the observer should face the wind, whirling the psychrometer 

 in front of his body. It is a good plan, while whirling, to step back and forth 

 a few steps, to further prevent the presence of the observer's body from giv- 

 ing rise to erroneous observations. 



The wet bulb — It is important that the muslin covering for the wet bulb be 

 kept in good condition. The evaporation of the water from the muslin leaves 



