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MASS. EXPERIMENT STATION BULLETIN 402 



Figure 3. The Intensity and Duration of Light Daily from January 15 to February 15, 1941. 

 The intensity in terms of percentage of the June 21 mean maximum is shown by the height of 

 a curve as measured by the scale on the left: the horizontal extent represents the duration of 

 light, which varies from 9 to 10 hours. 



