696. EXPERIMENT STATION RECORD. 



and determine the limit of its successful cultivation. A remarkable 

 example of their effect is to l)e found in the climatic history of Michi- 

 gan, where a half cciftury ago peach trees flourished and were rarely 

 injured by the cold; but after the lumberman began his work of defor- 

 estation Dakota blizzards made greater and greater inroads into the 

 State, the tender peach trees were killed along their path, and now the 

 peach crop has nearly disappeared. From the same cause the attempt 

 to grow peaches in northern Kansas has been largely abandoned. 



The third class of winds injurious to agriculture are those character- 

 ized by intense heat and dryness. 



The hot winds of the Plains occur over a vast agricultural area and 

 in some seasons do incalculable damage to all crops, and especially to 

 wheat and corn, which cover the greatest acreage. The area over 

 which they prevail extends from Dakota to Texas; in occasional sea- 

 sons they occur east of the ninety-fifth meridian, but their greatest fre- 

 quency and severity is westward of that meridian to the boundaries of 

 cultivation. An illustration of their destiuctiveness to agriculture 

 may be drawn from the statistics of 10 Kansas counties in 1888, which 

 showed a loss of 21,()00,(K)0 bu. of corn alone, due principally to hot 

 winds. 



Some of the results of an investigation of the hot winds of 1889 are 

 here given: They are usually from the southwest, and occur most 

 frequently in July and August. They generally continue for about 

 three days. The typical hot wind sets in at !) or 10 a. m. and continues 

 until about 5 p. m. In 6 hot winds reported the temperature ranged 

 from 100 to 109° P. The average humidity probably did not exceed 

 25 \)Qv cent. The force of the wind varied from a "moderate breeze" 

 to a "strong wind;" in one case it ranged from a "high wind" to a 

 "gale." No quantitative measures of the rate of evaporation Avere 

 received, but the rate was doubtless very high. 



In general hot winds do not materially affect the crops until by their 

 evaporative effect they have drained the soil of its moisture. All cir- 

 cumstances that conduce to diminish evaporation are most potent fac- 

 tors in preserving a crop of corn or wheat through a trying period. 

 Freedom from weeds, deep plowing, and frequent cultivation which 

 breaks up the capillary ducts in the soil, a sandy rather than a clayey 

 surface soil, a subsoil of hardpan which stores up the rain waters for 

 the crops to draw upon in critical periods — these are some of the condi- 

 tions which dinunish the rate (»f evaporation and delay the beginning 

 of the drought. 



Similar in effect to the hot Avinds of the Plains are those of the 

 Pacific Coast. These occur in the Sacramento and San Joaquin A'alleys 

 of California and to some exteut in i)ortions of Oregon and Washington. 

 In California these winds are northerly, and are often designated as 

 the "desiccating north wind." The greatest injury is done when the 

 north wind occurs in May and June, during the periods when the great 



