134 



AGRICULTURAL ECONOMICS 



In the accompanying table are given weather records to illustrate 

 the condition at different stations in the area: 



DATES OF FIRST AND LAST KILLING FROSTS 



It will be noticed that the shore belt represented by the Erie 

 records has a much longer season free from frosts than any of the 

 other stations. 



b) A MARGINAL CLIMATE 1 

 BY MACY H. LAPHAM 



The most striking and characteristic climatic features of the area 

 with which this report deals (western North Dakota) and which is 

 embraced within the climatic province of the semiarid Great Plains 

 are a restricted and variable annual precipitation, long, severe winters, 

 and a relatively brisk wind movement. The average annual precipi- 

 tation is rather limited for the successful production of crops under 

 ordinary methods of farming. The distribution of rainfall is, more- 

 somewhat fickle, varying greatly from year to year. The 

 greater proportion of the precipitation occurs during the summer 

 months as heavy local showers, often accompanied by thunder and 

 lightning. For Williston, the Weather Bureau records exhibit an 

 extreme variation in the total precipitation between the wettest and 

 the driest observed years of 15.9 inches (7.4 inches to 23.3 inches). 



While the area under discussion lies in the path of most of the 

 storms sweeping across the country from the Pacific Coast, the air 

 currents have been robbed of their moisture in crossing the slopes 

 and crests of thr rlcvaicd mountain chains to the westward. The 

 greater portion of the rain falls during the growing season, however, 



Adapted from loth Report of the Field Operations of the Bureau of Soils, 

 pp. 1169-73. 



