MAINE STATE COLL! 



of draughts of air. In order to avoid the effects of currents of 

 air, the vacuum ■ . : has been 



"This consists of a blackened bulb radiation thermometer . 

 in a glass tube and globe, from which all air is exhausted, Thus 

 protected from the loss of heat which would ensue if the bulb 

 were exposed, its indications are from 20° to 30° higher, than 

 when placed side by side with a similar instrument with the bulb 

 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 

 growing season has an important bearing upon the complete ripen- 

 ing of vegetables and fruits and likewise upon tLeir keeping 

 qualities. From the wide range of observations undertaken 

 Experiment Stations with radiation thermometers, important 

 tactions may reasonably be expected. I subjoin tables of 

 results from the maximum thermometer and the thermometer for 

 solar radiation, expressed in monthly averages. 



l5Si\ 



May. June. July. Aug. Sept. Oct Mean 



o o o o o o o 



Mean of readings, Sun Ther ...133.02 134.22 139 55 137.56 122.79 105.96 12853 



Mean of maximum temperatures 67.65 73.45 75-3© 73.72 71-23 52.73 69.05 



E solar intensity 65.17 60.77 64.25 63.84 51.56 53.08 59.18 



is:-:-. 



April. May. June. July. Aug. Sept. Oct. Mean 



OOOOOO DO 



Mean of readings, Sun Ther. .119.15 11945 128.81 13957 13525 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 58 



Excess of solar intensity 69.82 iS.29 60.80 62.84 6338 49X2 56.92 6057 



April. May. June. July- Aug. Sept. Oct. Mean 

 oooooooo 

 Mean of readings, Sun Ther. .106.78 119.19 129.4* 14055 129.55 12155 99.55 120-93 

 Mean of maximum Temp .50.65 62.48 72.17 76.68 7559 6954 54.18 6551 



Excess of solar intensity 56.13 56.71 '.' .' 6357 54.16 5151 4557 5552 



F: :m the above records it appears that the average excess of 

 solar intensity above that given by the maximum thermometer for 

 the growing periods of 1889, 1890, and 1891, was 58°.36. 



The season of gres.:e=: exc:--~ in :_i= regard was :_:,: of l c iv. 

 a season noted for the perfect maturity of fruits and vegetables. 



