150 MAINE STATE COLLEGE 



exposed to the passing air." By the use of this instrument the 

 amounts of solar radiation at different places and in different sea- 

 sons at the same place are rendered comparable. The relations 

 of solar intensity, as distinct from temperature of the air, to the 

 growth and maturity of crops are worthy of careful investigation. 

 High solar intensity maintained through the latter part of the 

 growth season has an important bearing upon the complete ripen- 

 ing of vegetables and fruits and likewise upon their keeping 

 qualities. From the wide range of observations undertaken by 

 Experiment Stations with radiation thermometers, important 

 deductions may reasonably be expected. I subjoin tables of 

 results from the maximum thermometer and the thermometer for 

 solar radiation expressed in monthly averages. 



1889. 



May June July Aug. Sept. Oct. Mean 



O OOOO 00 



Mean of readings, Sun Ther., 133.02 134.22 139.55 137.56 122.79 105.86 128.83 



Mean of Maximum Temp., 67.85 73.45 75.30 73.72 71.23 52.78 69.05 



Excess of solar intensity, 65.17 60.77 64.25 63.84 51.56 53.08 59.78 



1890. 



April May June July Aug. Sept. Oct. Mean 



o o oooooo 



Mean of readings, Sun Ther., 119.19 119.45 128.81 139.37 138.25 114.94 112.52 124.65 



Mean of Maximum Temp., 49.37 61.16 68.01 76.53 74.67 62.32 55.61 64.38 



Excess of solar intensity, 69.82 58.29 60.80 62.84 63.58 49.62 56.92 60.27 



From the above records it appears that the average excess of 

 solar intensity above that given by the maximum thermometer for 

 the growing period of 1889 and 1880 was 60.°02. 



Amount of Sunshine. 



The amount of sunshine as an essential factor in crop produc- 

 tion is worthy of observation and record. Observations were 

 commenced May 1, 1890, and the table below furnishes the sum- 

 mary for the six months following. 



Bright Sunshine in Hours. 

 1890. 



May June July Aug. Sept. Oct. 



180 186 216 193 126 133 



During this period, the average hours of bright sunshine per 

 day was 5.6 or 41 per cent, of the possible amount. 



